Rule #1: Apply anti-spatter spray liberally.
At Texas Metal Works, we buy Weld-Kleen anti-spatter by the 5-gallon containers and we use it all day, every day.
Before you work on a project, clean your table surface (you should be in that habit anyway) and then spray anywhere you might be welding near. You can actually spray down your whole table with it because it includes rust-retardant ingredients. So it will protect from BBs sticking to your table as well as help keep it from rusting.
Bonus tip!!! You can actually spray the anti-spatter directly on the parts you’re welding! Then make your welds right through it. It will also keep the BBs from sticking to your work where you’re welding!