To nail this achievement you need to score "Perfect" on every car in the game except Xzibits, while in the pimping phase make sure you have lots of money, that you always buy the most high end item and that you get to the secret supplier, if you're running low on time then don't haggle, just hit "RB" and pay the full price, you should have plenty of money during these events anyway.
Be sure to tackle the locations in a sensible order, drop everything for the Xzibit locations and the secret supplier points, if for whatever reason you feel that you've messed up, don't forget that you can restart the "pimp" phase, this way you wont have to play through the "cash" phase again.
Here's a list of the suppliers during the cash roam phase, just incase you're having difficulty finding any of them;
Marcia – In the same parking lot as the southwest blue cash token.
Andrea - On the north eastern side of the waterfront drive, just south of the tunnel, on the east side of the street.
Hari – From the southern music event, go west. The supplier is on the left before the first turn.
Leon - In the container yard south of the starting position delineated by the two triangle intersections, towards to northeast corner. You have to drive through the piles of containers (i.e., not on the marked road) to find him.
Alix - directly north of the southernmost music event on the dead end road the goes southeast.
Aiyana - in the west section of the map, when you exit the tunnel turn north and follow the road. It will turn southwest, then a sharp turn to the south-southeast. After you pass the two white roads on the right, the supplier is just past the turn to the east, on the north side of the road.
Jason - East of the starting position is a cruising event, with a white token north east from there. The hidden supplier is on the opposite side of the street from the token.
Sandra - 1 and a half blocks west of the northwest cruise event at the top of the map.
Zeke - At the northernmost tip of the map, east of the blue cash token.
Na - One block west of the southern music event, on the west side of the road running north-south.
Jewels - From the eastern cruise event, exit to the east and go south until the road ends. Turn left and the supplier is on the left.
Vinny - On the road to the north section of the map, right when you exit the tunnel the supplier is on the right.
Chadborn - At the intersection west of the northern music event.
Satomi - In the lower section one block north of the blue cash token.
Lucas - In the lower section, go east from the music event toward the blue cash token. About 1/3 of the way on the left, just before an auto supply store.