best thing to use to kill red wasp?

You have to kill the nest and since pyrethrim, recommended by Billy the Exterminator is tough to find, what I did with the dozens of nests in the roof of one of my out buildings was wait until it was 50 degrees, apply the wasp foam to all openings, and then seal them with steel wool. From dozens of nest last year to not a one this year. The foam keep[s them from attacking you and can kill them, the steel wool makes for a long term barrier that allows the roof to breath.

Get one of those sprays just for wasps, the shoot out to 20 feet and let me tell you, you'll need lots of space between you and the wasps!