QuiltE

Homasote .... probably the best way I can describe it is to say, think of paper mache, compressed into boards like plywood. It's quite hard, but soft enough to allow you to push pins or tacks into it. Will accept nails and screws without problem. 1/2" thick, comes in 4'x8' sheets and is quite rigid. I first was introduced to it via model railroading, as it is often used for the base when building model railroad systems. Should be available at building supply places.

Coroplast .... think of cardboard, but made of plastic. You've probably seen it used in lightweight signage, indoor or out. Look for signs that will be tossed out , and you have yours for free, though not likely they will be the full size, but a great way to try it out. Light in weight and semi-rigide, so easy to move around, or tuck behind/under furniture. Available from sign-making shops, either in 4'x8' sheets, or you may be able to buy offcuts at a reduced price.

Hope this helps you, Painiacs!