Costume Design Help and Advice for Beetlejuice spikes

I am new to cosplay and not very talented artistically; I have a friend helping who is but I cant seem to figure out the best material and method to create the spikes found on the Beetlejuice cosplay I am doing. I've attached 2 photos of the spikes.

I want to create the spikes out of some type of soft sponge foam that if the spikes hit someone they are just soft and compress easily. I bought a foam cutting heat gun but it just don't work good.

Any help on the best way going about creating "safe" and "compact" spikes and what material would be best and how to shape it is greatly appreciated.