Thank you to Igor Lesko, LPO:
Here is a low cost DIY foam cover shaping tool. It is Velcro hook, sticky, wrapped around an arbor. The larger the arbor/narrow Velcro, the easier it is to do. Both ends are stapled to arbor, so that it does not pop out. You can also use sticky dots, but will have to staple each one of them. Felt arbors do not work well for this, because the staples pull out. There is also a cylindrical arbor with recessed locking bar in it, that one is ideal for this application (from Fillauer). It cuts through all foams like a knife. As it is Velcro, you can transition safely from foam to socket or foot cover. If you go reasonably gently, it will not do any damage to both. Careful with going hard though – it will cut through foot shells. I use this almost on all my cover shapings. You can vary Velcro hook type to have finer or coarse finish.
Credit goes to a very nice Cambodian gentleman Sinovan. I picked this on him back in 1997.