Agree all above, I used to keep on top of that PM on both 80's that are on the road, just slipped my mind on the 96 model (until I heard the sloshing).
FWIW last year as a PM I sprayed 3M Cavity wax into the rocker panels of my 97 model making sure it didn't block any of the slit drains. Used...
Apologies to the OP for hijacking his thread.
I just had to use the zip tie trick to open up the slit drains on my 96 model's rocker panels. Hadn't thought about them for ? years and recently started to hear sloshing water but ignored it at first because I had a few gallons of water (jugs) in...
IME the sunroof glass assembly can/does sag over time, adding shims (available from Toyota or about any parts store) to the nuts/studs will raise it up and help the gasket seal better, although as mentioned it's not entirely waterproof.
If you remove the glass entirely there are other tricks...