i suggest u do this early, like doing it before beating the first boss. this way cops are heat 2 at most and are pretty slow. at heat 5 its a pain in the ass.
if ur looking to do this in heat 2 the pursuit needs to last 12 minutes. be aware the time DOES NOT continue in cooldown mode. once it pasts 12 minutes u can evade. you are going to have to sometimes slow down in order to keep cops. you may disable a few and have the back up cop time running. once it gets down to zero u can increase back to normal speed.