I'm reading that non lubricated condoms over shotguns with a blimp and furry should do the trick.
The audio assistant ("cable wrangler") or an intern is usually the one who is tapped to go to a very large pharmacy to purchase a
case of non-lubricated condoms when the sound kit needs a resupply. Needless to say, uptight types are horrified, most younger folks are
very impressed.
BTW, we used the condom solution when we shot a food fight a several years ago; it works quite well.
Not sure how to handle lavs... Maybe a ziplock bag over the transmitters
Really good lavs (Sanken, CountryMan, Tram and the upper end AT, Sennheiser, etc.) are usually fairly waterproof to begin with - they need to resist sweat and high humidity.
You'll have to cut and tape plastic baggies for the transmitters; they need to be VERY tight so they don't make noise or move around inside the baggie, and so you can use the controls. Put fresh batteries in immediately before you seal them up.
BTW, Lectrosonics don't need to be baggied; they are fairly water resistant on their own. There's a new transmitter from Lectrosonics is about the size of a fat matchbook and completely water tight. Needless to say, it's quite expensive.