Apparently, I am becoming famous for the opening line of this video. When I said "The best way to massage someone's but is with you elbow" I meant it. It is completely true. So get out there and try it. Start with lighter pressure and ask you partner if they want more.
You might consider this assortment of bath products, candles, and massage oil. It is a nice gift set that will perfectly compliment your newfound massage skills.