Brian,
Brady posted exactly what I followed - I used Sporty’s StudyBuddy for the PAR and Sheppard for everything else. Follow the Sheppard Study Method or whatever they call it and you should do great. I took my PAR first after going through the ATP elevates and sending them pictures of 3 90s or above that I needed to get my endorsement. Endorsements are needed for PAR, IRA, and CAX - You can get a complimentary endorsement through Sheppard Air for IRA and CAX, you’ll just have to give them a call, they’ll send you an email with some steps to take, and then they’ll send you the endorsement so you can take your test. I took a few weeks on the Instrument exam as it was totally foreign to me but the CAX and the rest of the exams were a breeze to study for - I think I took a week or so for most and only a day for the FOI (got 100% on FOI, much smaller question bank).
This thread also had some great info in it!
FAA Written Exams