I have tried the hot wire cutters and have stopped using them. They are slow, smelly and leave a smoth edge. I do all my foam cutting with a serrated steak knife,
There are many who use a hot wire/knife and like it, but I don't. You will have to decide. I like the speed of the steak knife and the rough edges it leaves. Seeing I carve all my rock details directly into the stacked foam and use very little plaster, I think I get better results faster with less mess.
I cut, slice, dig, gouge, scrape, and stab with abandon. The rougher I get, the better looking the rocks. You may find you like the technigue better than plaster.
That's my opinion.
