And you wondered why your brake was crap before? Tar is okay, is good to use as a last resort. But the pros of rim grinds are better preformance, work in the wet and dont completely ruin your pad. Plus with a grind you dont neeed to apply it every hour, you just whack it on it should last a few weeks to a few months depending on how harsh. Honestly get a grind man.
Plus it looks like crap is on your rim when you use it over time