Avoid using the slimy stuff, Us guys that change tires dislike it quite a bit for a number of reasons. Have had excellent results with dismounting tire,scrubbing inside of rim 'till spotless. Then coat with an epoxy spray paint in your choice of color. Contrasting colors assure full coverage, nobody gonna see it anyway, I used chrome yellow the last time. Has worked well. Now if I get used alloy rims for personal use I coat them all before ever mounting tires. Any leaks I have ever had since I started doing this has never been the rim. Valve stem holes have been a small PITA also.Before you paint remove valve stem. Started doing this coating deal 20 years ago when MB had a bad run of alloys. After using a "special coating" made just for this problem a couple of times, we decided that good old appliance paint was the same stuff that the snake oil guy were trying to sell at 4 times the cost. Cure paint as long as possible before tire remount. Hope this helps,later,rcs