[Carver]

I find surform tools very useful for shaping foam. However, the small fragments you create are irritating, they stick to everything. If possible, best used outdoors.
Here, I have used the surform tool only on one small spot, which is a „takeaway“ part.
I need to be able to lift that away to climb up to the table, step over to the paddock for getting access to the window...

   

For thin foam sheets, 10 or 20mm thick, a sharp, thin knife cuts nicely and clean, without creating very much scraps. This is what I have used here.
I will later cover with a tile glue/sawdust mix.

I am sure there are many with more experience of this!

Anyway, I hope this is understandable and helps.

Carver