I'm having problem with my old 3038 bogen ballhead. It's sticking a lot. It used to be sticky but now that it was exposed to a lot of dirt and sand it is locking frequently. Today I was only able to unlock it with a hammer! (really) The manfrotto's support guy advised me to send it to repair but I can't do it everytime it gets dirty. What lubrificant or grease would you recommend to use it in this ballhead? I would hope a sort of grease would help it against locking. Cheers.