What's the best bang for your buck in modeling supplies? A pack of disposable diaper changing pads. For just a couple of bucks you can get a marvel of a product. Super absorbent on one side, totally waterproof on the other. Put one of these down on any table and feel confident that the table is safe from paint, water, glue... or even baby poop. If you use the last one in your modeling efforts I don't want to know about it.
I use these to model in our kitchen on our granite counter top or our kitchen table. Also up in our office on our desk. Several years after discovering this trick still no problems despite spilling all sorts of stuff from paint to bourbon.
As a bonus, they usually have some cutesy pictures like fish or teddy bears you can deface with eye patches and horns if you are taking a break.