How to take Triamcinolone. Apply a thin layer of lotion, ointment, or cream. Then, rub it in gently. To use the aerosol, shake the bottle well and spray onto the affected area for about two seconds to cover a spot about the size of your hand. Cover your eyes if you spray the medicine near your face. If you’re using the dental paste, apply a thin layer (just enough to cover the mouth sore). Follow your doctor’s instructions carefully when taking this medicine. Don’t apply more or less than is prescribed.