Has anyone recently used one of these and did you have any problems? I have bought two containers of Ducks Back 5 year sprayable stuff as recommended by Cuprinol but have yet to have any success. It goes from the battery not being able to hold any charge to only getting a feeble trickle of the actual stuff coming out of the nozzle and then having to wash the thing out all over again which is so messy and I have yet to get it on the fence. Any tips gratefully received.