[cyclohexane]

I've drowned my 70-200mm unprotected in a downpour without ill effect. I'd just screw-on a filter to protect against front impacts (done this before, no issues with breaking filters, but I only took one hit from a less lethal projectile), and use the hood. Also, the whole point of suggesting a 70-200 was to get him out of the path of the paintballs. =)