Rub meat with a layer of yellow mustard. This the holding agent, and will help the rub stick to the ribs. Mustard will cook off and you won't taste it when done.
Rub on prepared meat. If you can do this 24 hours in advance, great. If only a few hours prior, that works too. At the very least, give it an hour between the time you apply the rub and put this on the grill or in the Solar cooker.