Spatter: Leather, grain, full.
I dunnow the situation, but couldn't he wear a leather shop/welders apron, then drape a leather skin across the arms of the wheel chair for added protection? Welders cape for the upper body.
Halon is nice an all, no residue to clean up after the fire is out. But it's hard to come by as when it hits flame it produces a toxic chemical I understand. And it works by depleting oxygen, may not be ideal if your buddy can't move outta the way quickly.
Wood drafting table would work... for a few arc strikes. Wood kinda smolders in the presence of hot metal. Don't ask me how I know this
See Halon and spatter above.
Rick