With regards to tar, I've never understood how you can just go 'dig it out of a road'. When i used tar i found a good load of it in the middle of the slabs that made up the sea wall. The tar in roads is combined with a bunch of rocks and shit so it isn't any good. When you do get hold of some tar it has the same consistency as really old chewing gum that's been stuck under a table for a week. Hard, but you can dog your fingernail into it. The best way i found to apply tar is a dozen little lines in the same direction as the spokes (pointing towards the hub) this way you get a even spread when you drag your brake. Always put a little on and add more, you can't remove tar from rims easily so don't put too much on. And put even less on in hot weather. Don't spin your wheel and hold the tar against it, or colour your rim 100% black with it. You end up with waaaay to much on.