I am going to try making a cake with a zombie hand coming out of it, any thoughts on what would be the best medium to use? I was thinking RKT covered with fondant but then thought I might try modeling chocolate (which I have never used before).

how about rkt covered in modelling chocolate? If you use solid modelling hcocolate it will be REALLY heavy!

I agree, RKT seems like a good option. I'd smash the RK's really good before adding the marshmallow though, easier to cover and less bumpy.

Wow - what a timely thread! I was going to post this very question today. I'm doing a zombie hand, too.

I was thinking of RKT covered in marzipan, but I'm not sure if marzipan is a good medium or not. It's naturally closer to skin tone in color, so painting it up with moss green and black shouldn't be hard. I just don't know if it will dry too much or how thick to roll it.

Any suggestions? Is marz a bad route?

I've done this w/RKT, and then 'spackled over' in BC to smooth out some of the bumpiness before covering w/fondant. Worked great.