in my history of doing this lol, i have used RIT dye. it works really well. first i pin about an inch below were the part on were the fabric sorta starts to fade off to the original color of the fabric *ie in the yuna sleeves i would have pinned it were the pink started flowing back to white* then i put the fabric in the dye *always test first u might have to dilute it a lil to get the lighter color* and i leave it there for a few minutes the reason i pin it is so that i insert the fabric till were it is pinned and then let it bleed up just a lil for the fading effect. i only leave the first part for about 10 minutes then after i am done with the lightest color i pull the fabric up so that i could dye the bottom of the fabric a darker shade. i leave that for about 45 -60 minutes. ok i hope that helped a lil bit ^.^
about the foam, do u mean the craft foam?