My friend Mike(SGTMAJMVJ) and I made a 1/16 bridge the other day for our indoor battlefield but some of the tanks are having a hard time going up it due to spinning. What kind of spray or material do you all recommend to put on the bridge to help grip? We obviously don't want to put anything on there that could possibly damaged the tracks. the material we used for the road itself is roofing shingles and its just too slipery.