Hotshot Racing

This will be longest grind in game. You can check unlocking conditions for any part in customisation menu but they are basically same for every character & car. To make this short.

1. You have to win any Grand Prix with every car of every character (so it's 8x4 GP's).
2. Have 500 secs of drift, 300 nitro uses and single 5 sec drift for every car. Depending on yours skill it's like 10-12 3 lap races for each of 24 cars.

Once you have other skill depending achievements grind for this one should take around 20 hours depend on skill. On higher difficulties have higher top speed..

I thought I would write my own guide for this so I can make it more clear to everyone what you need to do and to give my own tips.

Firstly to see what you have left to do, you can either look at the customisation options on the main menu or look on the end of race screen while using a particular car.

To unlock all the customisation options this what you need to do.

Each car has it's own set of objectives to unlock all their customisation options, but every car has the same objectives, these are:

Win a GP (GP mode only, any difficulty)
Boost 10 times one race (Not Time Trial)
Boost 100 times (Any mode)
Drift for 5 seconds in one drift (Not Time Trial)
Drift 20 times in one race (Not Time Trial)
Drift for 250 seconds (Any mode)
Drift for 500 seconds (Any mode)
Drift 300 times (Any mode)

If this is one of the last achievements you need and you have you done all the Expert GP achievements, the best way forward to just do all cars winning a GP on normal difficulty on the cars you have remaining to do that objective first.

The AI cars barely drive away from you on normal difficulty so you can easily keep up. For me, the drifting objectives seem to take the longest, especially drift 300 times, so while you're doing the GPs just constantly drift, straighten your car up to stop the drift and drift again, even in the straights.

Every time you straighten your car up that will count as one drift, but you will need to make sure you don't switch the car into the other direction while drifting otherwise this will continue the same drift and still count as one. How do you know that you haven't continued the same drift? That's easy, if you're car still has smoke coming from the the wheels with no gap in it, it's still the same drift. Also your boost meter in the bottom right hand corner of your screen, if it doesn't show +1 again you're still doing the same drift.

While you're doing that, chuck the odd boost in, don't let your boost bar max out and just completely ignore the AI. When you get near the end of the last lap, save a few boosts and just boost up to and over the line, make sure you have a boost to boost over the finish line with, you should win the race. Do the same for all 4 races and you should win the GP with some progress towards the other objectives!

*Boss GP has 4 lap races instead of 3 which would help make get the below objectives easier*

While you're doing the win a GP objective make you get and you should have:

Drift for 5 seconds in one drift during a race
Drift 20 times in one race
Boost 10 times in one race

This will leave you with the any mode objectives left. After the GP one is done I recommend heading to Time Trial, although you can carry on in any mode you wish. Time Trial gives you 4 boosts every time you cross the line so that will make the boost one a lot easier, you can still get boost from drifting to! Just keep going around drifting constantly in the straights also and boosting until you think you've done enough then end the Time Trail.

When you end a race or time trail, do not click continue on the screen where it shows how much money you have, as after a couple of the seconds your objectives will show up on the right hand side as either completed, will have disappeared (as in you've already finished that objective) or how much progress you have towards it.

Last but not least, the special palletes! There are an extra set of palletes which are not tied to any particular car in the customization section, (so if you're at 99% this may be the ones you've missed).

Two of the objectives for these are:
Beat a staff ghost in each zone (Time Trial)
Win an Arcade race on Expert difficulty (Arcade Mode)

*I'm unsure if there are more objectives for these special palletes as I've already done them, if I've missed any please let me know in the comments, thanks!*

So in order to do this one you need to beat staff ghost in each zone in the game.

There are 4 zones:
Jungle
Desert
Coast
Mountain

So all you need to do is beat a staff ghost on one track in each of these zones. Any track can be chosen in a particular zone and any car, so I would recommened the Super F-90, fast and handles well.

If you've done all that, you should have unlocked everything!

Extra Information:
If you're low on money, the quickest way is to play Drive and Explode, 3 laps, normal difficulty. Make sure you win, you will get $23,000 every time!

Hope this all helps! Thanks for sticking with the guide if you've read this far!