Take a wire wheel and run it around the bead area of each rim - the dust will fly for sure. Get all the whiteish-gray crap off. Then clean the rubber of the tires that mate to the bead area. Wipe clean with alcohol. Then use a good quality bead sealant that has some body to it. Brush on a nice coat all the way around. Install tire and seat bead - give it a little while to set up. Check with soapy water for bubbles. Also, replace the valve stems and clean all the crud around their mating surfaces too - emery cloth on a screw driver works well. You can put a shmear of sealant on that as well.
If that doesn't work, go to FB MARKETPLACE and get a set of used wheels and be done with it.