When stamping with fabric paints and thickened dyes, it is important for the stamp to be fairly deeply cut. Most stamps are made to be used with ink (a thin liquid) on paper. Fabric paints and dyes will clog the tiny designs and obscure the design. Foam stamps are excellent. If you make your own stamps, be sure to cut them at least ¼" deep. The fabric paint or thickened dye needs to be thick and not runny. Although everyone has an impulse to simply dip the stamp into the color, this will most likely give you an unsightly blotch.
Cover your work surface with plastic, freezer paper or newspapers to protect it.
Place extra newspaper or other paper under your fabric to absorb any excess color.
Place your fabric down and tape it with masking tape to keep it in place.
Pour the fabric paint or thickened dye in part of a flat plate (the plate can be paper, plastic, ceramic, glass or metal – old tin pie plates work great).
Using a foam brush, pick up a little of the color and pat it dry on another part of the plate until there is an even coating on the foam brush.
Pat the color from the brush onto the working surface of the stamp so that there is an even color throughout. You can mix colors during this process, blending several together on the stamp.
Lower the stamp straight down and press it with your fingertips to get a firm impression. If the stamp is unbacked, work your fingers along the whole stamp. If it is backed, rock it slightly.
Lift the stamp straight up.
If you are overstamping the designs, let the first layer dry first. Otherwise you may smear the colors.