Drain hole cleaning methods?

Great image redness :cheers:. Update: Cleared drainage area. After heavy rain last night came to wet carpet again:banghead:! Found large gap in windshield weatherstripping/gasket, off to auto glass shop tomorrow. Pulling seat, carpets, and air vents next weekend (when I have access to a garage) to search for rust.

I have kept this car stored dry (for the most part) since I bought it in 2008, but water most likely made it in with previous owners. Fingers crossed the floorboards aren't too bad:pale:. The trunk leaked and I replaced the weatherstripping first chance I got, I also removed the minor rust found under the spare. Hoping for an easy fix for any damage I may find under the carpet as well.