Painting the Purple Iris
Step One: Preparing reference art
After developing your composition into a working sketch, or selecting a photo for reference begin by drawing a grid on the reference art. (You can draw your grid on acetate and tape it to the reference art, or if you are using digital photos on your computer, import your photo into a page layout program, draw your gridlines on top of the photo and print out a reference print.
Tape your paper to your support with masking tape on each of the four corners. Using at least #140 paper avoids any problems with warping as the paper expands and contracts from the moisture in your paints.
Lightly pencil an enlarged version of your grid on your paper.