When using a spice rub, wet or dry, sprinkle or spoon it over the meat, then gently massage in the seasonings to make sure they adhere.
Allow time for the seasonings to penetrate. Rubbed meats can be cooked immediately, but for more intense flavor, refrigerate rubbed meats at least an hour, or larger pieces overnight.
To prevent contaminating your spice rub, spoon out the portion you'll need before rubbing it on the meat; if you need more, use a clean spoon to retrieve it from the jar. You can also prevent contamination by using a spice rub shaker (a repurposed empty spice jar will do) to apply the rub to your meat.
Use an empty pepper mill to grind spices for your homemade spice rubs. Then there is no need to clean the coffee grinder!