Hey Corinne,
Good to hear that you are still hanging in there, and that you have migrated your masking and tracking to AE, although still on CS4.
Best advice: In AE CS4 you have a free version of Mocha included – nothing like the version that you will find in the latest CS version.
There is a video, amongst many, to get you started here:
“After Effects CS4 Essentials Mocha Tracking Application”
https://youtu.be/bC5hz-Lpfw4
If you want to go really advanced, BorisFX is offering you a 14 day trial of the latest Mocha Pro 2022 standalone:
https://vfx.borisfx.com/mocha-pro-free-trial
PLEASE NOTE THE WARNING: Any Mocha projects created in the trial version, can NOT be opened later in the paid for version.
Also, later versions of Mocha have a lot more functionality, and a steeper learning curve,
With that in mind, give the free version of Mocha inside AE CS4 a spin first, and hopefully that will sort you out.
Good Luck!
Mads