I bought an essential oil burner at my local health food store. It uses a tea light candle and has a small dish on top. When I want to test a blend, I fill the dish with water, add my EO's in the desired ratio, and let the fragrance fill the air. A tea light lasts about 3 hours, and that is a good time to tell if the blend works as expected. If not, I tweak and try again. No more guessing with toothpicks or cotton balls!
Good luck!