Monty spray is much better than tar(in my experience).Tar has a lot of "-", one of them if you salve a lot of tag on rims, pads can adhere to rim.
Spray also has a "-":he is ends fast, if you ride a lot of time every day(( and I heared that some type of pads bad matched with spray...
try to use grind with hard pads...i think that you love it combination))
good luck!