When it's warm outside, just head to the nearest roundabout and drive around it going gradually faster. You should be able to scrub them in in a few rounds (on side at least). On my straight-sit-up bandit I could have scrubbed them in in 1 min if I had asphalt in front of my house

Last time I had to ride 1,5 mile to do a couple of rounds and good to go!
