You can raise your bounty as much as you want and complete that part of your milestones. First get in a pursuit and then find a ledge (ex. on top of the buses at the bus station) go as closes to the end of the buses away from the up ramp as possible without falling off and without a cop following you up the ramp. Then sit there and watch the cops go crazy. It's better if your heat is 2 or up as the lower level cops will sometimes lose sight of you and you'll cool off. At higher levels though the police will hover below you ramming into each other and everything else. This destroys their vehicles which in turn raises you bounty and length of your pursuit. You can sit there as long as you like but check behind you periodically just to make sure one of them hasn't gotten smart enough to come up the ramp. The highest I've gotten off one pursuit is almost 6 million bounty.