Are there any alternatives to polystyrene for lost-foam cast

I think I know how to go about building my prop sniper rifle now. Lost-foam casting!
But I was thinking that maybe polystyrene wouldn’t be that good of a sculpting media. I really want to go hard and artistic on the master mold.
BTW I’m really super new to this. I literally just discovered lost-foam casting an hour ago in YouTube.

Can I use a denser grade of EPS (extruded polystyrene) foam sheet for wall insulation? Will that give me smaller cells? Or should I use a fine grade meshed sand? Which one will improve the casting’s final surface better?

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