Project CARS 2

You unlock the ability to do these factory events by driving the manufacturers vehicles in events, races, or time trials. You can visit the page to see your progress toward unlocking each affinity. Each requires an introductory event and then three fixed events in a specific manufacturer vehicle. Once you get through three of these, you will get the achievement. Your first will count toward your "lifetime goals".

These are lots of fun but you'll probably need to see the car and track and go practice on your own.

These were my 3 manufacturers, all 3 are easy to get the affinity with as they have cars in plenty of the divisions even early on, try and use them whenever you get the chance in the invitational events too, all races I state here are at their shortest possible length.

Ginetta

#1 - 5 laps of Snetterton 300 in a GT3.
#2 - 5 laps of Zhuhai in a LMP3.
#3 - 5 laps of Sportland SUGO in a G57.

Ford

#1 - 6 laps of Lydden Hill Rallycross in a Focus GRC.
#2 - 3 laps of Mount Panorama in a Falcon V8.
#3 - 8 laps of Le Mans in a GT LM (set opponent difficulty to 0 and drive 4 laps yourself then switch to the AI driver in the pits if you can't be bothered doing all 8 like I couldn't.).

Porsche

#1 - 12 minute race around Hockenheim Classic in a 935.
#2 - 5 laps of Algarve in a Cayman GT4
#3 - 3 laps of Nurburgring GP Circuit in a GT3R

While I'm not sure about any of the others definitely avoid the Honda one as the 2nd race is 10 laps of Road America.

If anyone knows of any other manufacturers that are shorter than any of these let me know and I'll add them in.