One of the best things about a windsurfing van is that it becomes practical to carry everything you might need. Here are two key items, and an experiment. The hand brush gets used all the time to keep the van floor relatively sand-free...it's also good for getting sand and dirt off of wet boards. The rubber mallet for stuck fins and anything else that needs a loving impact. The item to the left is a $2 bottle washer...made for cleaning the inside of wine glasses etc. I thought it might be good for cleaning out masts when they get particularly gritty. I've only used it twice (I keep my gear reasonably clean) and it was helpful but not crucial.
Thes things are literally jammed between the inner and outer shell of the raw van, where they are held firmly in place. There is a danger of putting bumps in the outside skin of the van, but I haven't had any yet.