Haven't used master bond before but from the description it sounds like the stuff I've heard recommended by a few people Tom.
Splitting them's not hard, take it easy on the oven temp though (90-100 deg c for 8-10 minutes is plenty, check them after 5 or 6 minutes, and if they begin to harden when you're splitting them fire them back in for a minute or two).
Have you checked the obvious, that the bulb holders are properly seated into their holes and there's no gaps, and that there's sponge bungs in the breather tubes?
Polishing is normally only required on the outside of the lense, it's worth taking them to a detailer or body shop and asking them to wetsand them with a very fine grit, then machine polish with compound, they'll come up like new.
Edit - Supraloopy is the trader/hobbiest that was doing them.