I figured you folks have been down this road already, so I've come here to ask, rather than perhaps the container planting forum.

I want to waterproof the bottom of some standard clay saucers so they won't ruin my furniture. I noticed that now they sell them that way, (Gee, can't you tell how long it's been since I've been gardening! LOL!) but I have lots of old and free saucers, and I'd like to waterproof some of them.

I also want to waterproof some wood and metal buckets and other odd items that might rust or rot if I used them as planters. I'm not concerned about chemical leaching, etc. I wouldn't grow edible plants in them, but if I worried about those things, I couldn't live at a busy intersection in the middle of the city.

Naturally, I want to buy one product that's cheap and will accomplish many tasks. Maybe I'd like to also find some camping and fishing applications for it. I'm not up on all the new-fangled products that are on the market now, so I'm sure there's something out there in the plumbing or carpentry department or elsewhere that would be great for this purpose.

I assume something I could paint on would be cheaper than something in an aerosol can. I'm hoping it would last in a can for a while if I keep the lid on tight, so I wouldn't have to use it all at once.

Is there anything available that is also thin enough to put in my own sprayer? I'm only talking small quantities for a quart-sized houseplant sprayer, not a big-time gallon-sized pump and hose sprayer. (I can dream, can't I?)

I'm sure 3-M or the like has "been there, done that".

What's the best thing for me to buy? What exists and WORKS?

Many thanks.