Modification Dyeing Additive Mods

Dyeing is usually done with boiling water to ensure the pigments go deep enough. I am not sure how well foam clay holds up to that? I also just did a quick search in regards to how well it holds up getting wet after it dried, and it's usually advised to waterproof it with something like mod podge. So submerging it into boiling water for some time sounds to me like a no-go.

Aside from that, usually additive mods take dye differently than resin. In case of apoxie you usually end with the modded parts looking darker/more intense than the resin surrounding it.

For floor draping ears I might use different material all together. Either sewing them (I imagine something like long, big, floppy bunny ears but a sketch would help here), or silicone casting. That would require sculpting them separately first, then molding, then making a silicone cast, ending up with finished ears you can pull over the existing ones on the head. Certainly not beginner friendly

 

Another way of colour matching the clay is to tint it before you sculpt with it. I am not familiar with foam clay, but with with milliput or apoxie you can add a few drops of paint /pigment/pastel to bring it's colour closer to resin - that way you can do the dye job safely before the additive mod.

 

The issue with doing the dye job BEFORE the modding though is that a good, smooth mod requires quite a bit of sanding. Or else you won't get a really nice, smooth transition between mod and resin.
If you first dye, then mod, you will pretty much end up sanding off the dye in the surrounding area

I'd also add, even if you dye and go with mod before or after...the airbrush is still most likely needed to make it look good anyway. Dye jobs are mostly to keep some posability and make chips look less intense (airbrushing a white doll purple will mean every scratch will be white, dyeing it purple before airbrushing some more purple on top means your scratches are still purple as well). You just gotta decide which way of doing things would work best for you.

 

As someone who has expierence with Apoxie and Foam Clay.... I wouldn't use Foam Clay for that kind of mods. You can't sand it the way you would be able to sand apoxie you have to sculpt super exactly from the start down to every pore, it shrinks (!) during curing and it might be flexible but you need to coat it with a flexible primer to keep it from breaking over time.

I haven't tried to dye it but well.. you have an air hardening foam, not a real clay, I have yet to test how to paint it. Yes it's cheaper but as said it's basically an air drying foam, not truly a clay. It's super squishy even after drying and you can peel it off the surface again you stick it on even without much effort (it's one hell to remove it when it sticks to each other when it's still wet though).