Check out the autogeek forums (a detailing forum behind the autogeek store front) they might have postings in your area for local details or reccomendations. I would say you can take your convertible through a brushless - I mean the top doesn't leak does it? Or if it does and you don't know it you would find out quick - If you have the spa\ce (garage) I would look into waterless washing - all you need are two buckets a sponge and some microfiber towels to dry off.