As promised, here's a step-by-step explanation of how I use Letraset's AquaMarkers to color illustrations (you could certainly use this process on stamped images as well.) This is a super long post so it's probably best to get your coffee ready and settle in...I wanted to be as complete as possible!
First, gather your supplies. 1) One of the keys to success with AquaMarkers is sturdy paper that can take abuse. I've found that 140 lb cold press watercolor paper works well. If you're stamping, the smoothness of hot press paper will be necessary.
2) The second thing I've found essential is a slightly stiff brush. Normally, I keep my acrylic & watercolor brushes separate; no matter how well you clean, acrylic gradually destroys a brush's flexibility. However, for working with these markers, I need to be able to push that stubborn color around so I pick a brush from the acrylic jar. And since it is easiest to work small sections at a time, small brushes are nice. Here I'm working with a quarter-inch angle shader and an 1/8th-inch flat for really tiny areas. 3) Letraset's AquaMarkers of course and 4) a swatch card. Don't rely on the inserts in the marker's package. Make a little chart of all the colors so you can compare the hues and intensity rather than having to waste a lot of time guessing. 5) not shown - water & paper towel.
Step 1: Draw something in pencil on your watercolor paper. You could also color a stamped image; just be sure to use a waterproof ink.
Step 2A: Determine your light source & choose the lightest shade of the color you'll be using. Here I'm going to be coloring my little ogre green so I begin with "Citrus." Apply lines of ink in the areas that would be DARKEST (i.e. farthest away) given the position of your light source.
Step 2B: With a damp brush, and working from the top down, begin to pull the color out towards areas that would be LIGHTEST (i.e. closest) given your light source. Typically, I work an area at a time as the longer this ink dries, the harder it is to move. For purposes of this tutorial, I went ahead and added all my color lines so you could see what areas I targeted.
Step 2C: Here's the first layer of color complete. Now here's a big tip: LET THIS DRY COMPLETELY IN BETWEEN EACH STEP. AquaMarkers perform more like a dye than traditional watercolor so if you add color when the paper is wet, the color gets down into the paper's fibers and is MUCH harder to move around. In addition, you'll damage your paper more than desirable trying to get that color to move. As far as I can tell, there's no way around paper pilling with these markers but you can keep it to a minimum by letting each layer dry.
Step 3A: Repeat the previous steps with the second darkest shade of green, "Spring Green." Here I've laid in the color, with slightly smaller strokes than layer 1.
Step 3B: And here's that 2nd layer of color pulled OUT OF THE DARK areas TOWARDS the LIGHT. Again, be patient and let it dry. (I usually work on multiple illustrations at once.)
Step 4A: Here I'm working with the darkest shade of green, "Fern Green." Again, lay in the color but just using fine lines. You can use the bullet tip for this or use the brush tip with a light hand. Think of that color you put down as a little well to draw from as you pull from it with your brush. You don't want the darkest layer to cover up previous layers.
Step 4B: Here's that Fern Green completely brushed out and drying. At this point, I felt like the tummy was losing some of its light so I wet the area a bit and used a paper towel to lift out some color. (See Step 5A for the results.) The ultimate goal is an illustration with multiple, identifiable layers of color so each time you add a color, add a little less than previously so your lightest shade doesn't disappear.
Step 5A: I like to add in another color to deepen shadows and make them more visually interesting. Any of the really light colors in the AquaMarker palette will work but I'm partial to "Frost Blue." Again add the color in areas farthest from the light source. Brush out that shadow color just enough to feather its edges and prevent it from looking like a hard line.
Step 5B: Here's the Frost Blue shadows complete and drying. Look at the difference in those shadows with that fourth color added...so much more dimensional!
Step 6: Now our little ogre gets his hair colored in the same manner as the body but using only two colors: "Cherry Blossom" and "Rose Carmine."
Step 7: AquaMarkers are transparent so they can be layered to form new colors. Here I've taken the "Citrus" marker and added stripes. Again, let each layer dry before proceeding.
Step 8: Here I've outline the ogre with a black Micron. (Obviously, this is an unnecessary step if you're working on a stamped image.)
Step 9: Sometimes, after the outlining, I see little areas that need a little more shadow like under the arms, under the eyes, and the soles of the feet. I deepen the dark areas a bit further with thin lines of the darkest green, "Fern." Again, I use a slightly damp brush to soften those hard lines just a bit. If you let each layer dry, you can continue to push the depth of those shadows and the more you do so, the more three-dimensional your illustration will look.
And the little ogre's all complete! There's no doubt that AquaMarkers are a labor-intensive tool but with practice, it does get faster and the results can be very luminous & interesting. I actually use this exact process when working with traditional watercolors or colored pencils. And speaking of colored pencils, when you are done with the markers, you can use colored pencils on top to add additional details and shadows. Just don't try that until you know you won't be using markers again because the wax in pencils repels water!
Please let me know in the Comments if this tutorial is helpful and if you have any questions, just ask! Now go play!