Dirt Rally

There is a way to make this a lot less painless to do and much quicker.

Depending what car Rallycross car you buy, change what perks you need as per the car brand.
This guide is based off the Renault Clio 1600's Rallycross car.
Go to Career>Team Management
The amount of perks you can choose depends on the amount you have unlocked with your engineers.

Crew Chief -
Perk one = Rallycross 1600s Vehicle Class - 5% reduced upgrade times.
Perk Two = Rallycross 1600s Vehicle Class - 10% reduced upgrade times.
Perk Three =Rallycross 1600s Vehicle Class - 15% reduced upgrade times.

Engineer 1
Perk one = FWD Vehicles - 5% reduced upgrade times.
Perk Two = FWD Vehicles - 10% reduced upgrade times.
Perk Three = FWD Vehicles - 15% reduced upgrade times.

Engineer 2
Perk one = Renault Clio S1600 -5% reduced upgrade times.

Engineer 3
Perk one = French Manufactured Vehicles - 5% reduced upgrade times.

Engineer 4
N/A - Does not matter, you have no more classes relevant to pick for your car.

As you can see, this goes off the basis of you using the Renault Clio. Depending what car class you use in Rallycross, change the guide accordingly. For instance, if you choose a Rallycross Supercar, you need to make sure the perks you pick are relevant to the car you pick.

So if you use the Ford Fiesta Rallycross, make sure you pick British Manufactured vehicles for Engineer 3.

Hope this helps.