Patched and no longer working as of November 17, 2021
There is an easy way to boost for Super Wheelspins. All you need is 40,000 CR and 5 Skill Points for each spin.
Go to the Autoshow and purchase the 1945 Willys MB Jeep for 40,000 CR.
Go to Upgrades and Tuning and then select Car Mastery.
Purchase the first skill, the one to the right and then the Super Wheelspin above. This will cost 5 Skill Points. You will get 7,000 XP from the first skill which will help unlock normal Wheelspins.
Keep doing this until you get a Forza Edition car. It is random but this should help speed it up.
Tip: Use whatever car you are comfortable with and can bank a 500,000 point skill chain. This will unlock the max of 10 Skill Points in one go.