With other cars, I have put A4 paper on the lights and left them on with a battery charger connected and the rear covers removed. They get really warm. I tried it with black card one and they got too hot so white paper is best.
I put big bags of silica gel in my lamps. I got them from a camera shop on ebay. they are about the size of a packet of KP nuts from a pub, not the little sachets you get with a pair of shoes etc.. They do seem to have helped but you need to add them when already dry as a preventative measure rather than as a fix..
100g IIRC
http://www.ebay.co.uk/itm//141205157393