Masking large areas is exciting; lets take flowers as the subject matter. Watercolor is a particularly sympathetic medium given the vibrancy of its colors and the subtle blended effects that can be achieved: approach the subject as you would any other subject matter. See it as an integral and integrated part of the whole picture. Plan the composition as you always do. Make thumbnail sketches to help you consider what you want in the painting. Sketch in broad outlines what you want rather than tentative marks. The pencil drawing allows you to elicit the painting from the broad compositional structures you have identified.

Next decide where the lights and darks will go. Here you have two choices, one is you can start laying down your tones very carefully the lightest areas first or you can do another technique by masking off the lightest areas. The nice part of the second theory is you can work and not worry about getting to dark to quickly. Think about where you want the masking fluid and be very careful of its placement. That way with the masking off you can see the peddle of the flower you chose. And later you can lay the color wash of the pedal and add a brilliant sparkle with this technique. On your first try please try to pick something simple and build your understanding from there. Please remember to allow you paint to dry between coats, if I am wanting to work faster I keep a hair dryer near, which does speed up the drying process, but do not put it on high, especially if you are using the masking or the wax.