Hey Gary,
I always leave my #20 sit for about 15-20 minutes before wiping it off. From my understanding, this should be long enough for it to bond properly.
I know what you mean about the clerks at Lordco. They know that I am very particular about getting sealed bottles. One local store (not Lordco), seems to always have open unsealed bottles that are missing a fair amount of product. I have a feeling that a stock boy is getting a few "samples"!!

I now have to tell the store when I order a product that it must come in sealed or I will not accept it. It is also a safety issue. I did have a couple of problems with Lordco and old stock. You may want to check and see how old the product is before you buy it.
Take care,
Tim