This is better used in a group with others helping you, otherwise
by yourself, I don't think it's very effective. Basically your 
group needs to place markers on two CLOSE 'chop shop' locations
where you drop off stolen cars (but keep in mind it takes a few
minuets for a drop location to allow you to drop off another vehicle).
Then at both drop locations, park a car on both sides of the street 
so that they stop MPC drivers in close proximity to where you'll be 
drooping off the cars, thus allowing a line of cars for your quick 
paced needs. Now, the most important part is to start any mission 
that pops up. When you start the mission, drop as many cars in the
prepared locations you've decided as quick as you can, before the 
mission ends. This, on average, with four players altogether on 
your team will accumulate 200 standing points: 400 with practice.
Considering if you start missions one after another, you'll level 
up rather quickly. Enjoy your high level characters!