I had real problems earning points and keeping them at first, searching for a guide or anything to do with them was scarce and not much help except for lists of what each one was and what you do to earn it. Like this one Skills | Forza Wiki | Fandom
It is good for a lot of info on skills but what I had to learn was how to keep a streak running until I got 500,000 points, which is 10 mastery points and the most you can earn in one skill streak anything above that is wasted, also you can only earn 999 mastery points.
The trick is to get different skills constantly, I depend on on air, drift, and wreckage to keep a streak running, anything extra I get is a bonus.
So a hilly area with bushes, fences etc is the best and the best I have found is around Croftdale Farm house because there is nothing solid in the area, looking at the map you go right from the house to a grove of trees just after an intersection and back again constantly.
Drift back and forth the whole time while crashing fences, trees and bushes, dont go near the road or you might crash into a car and lose the streak, the hills help you drift naturally. In this way I can get 500k in 3 to 5 mins (its different every time) with the Hoonigan RS200 because I upgraded the mastery to the 7X multiplier on it. A skill song gives me 10X because I have the the stereo mastery skill as well as the Huntsman lodge.
So
5X you need to earn 100k points.
6X you need to earn 83,333 points
7X you need to earn 71.428 points
10x you need to earn 50k points
There are a lot of places and just outside the festival area there is a small valley with fences which is good too.
I hope this helps someone and if you already know it that’s great,
The beech with the fences makes it easy to keep your score going. Just stay near the fences.
Mini drifts.
If you see you are going to lose your momentum, just make a mini-drift if you are on the road, to keep chaining skills. Thats all you need. Honestly its too damn easy to reach 500.000 points once you played enough. As i said, chain skill after skill and if you run out of time make a mini-drift that will allow you to continue the skill chain. Thats it.
I do it all the time, in fact, with hyper cars you can just go to the main highway on the map, and drive as fast as you can passing trough traffic. Making near misses, speed skills, threading the needle, and daredevil skills is enough, and again, if you lose momentum, just make a mini-drift and keep going lol. Pretty easy.
Also keep in mind, you cant chain skills if you do three exact same ones in a row. That wont count. It doesnt matter how many fences you destroy, you need to do something in between or it wont count.