Roof Caulking

I would avoid Dicor. If will work, for a period of a few years, then you'll be doing the job again. If you're lucky you'll renew the seal in time before it fails and leaks.

I removed all the old and prior owner's resealing attempts with various caulks and sealants and tape with Eternabond. For areas that can't be taped I used Eternacaulk Sealant that has worked very well for the past 10 years on my coach which is out in the weather 24/7. Both the tape and sealant are safe for EPDM, TPO and many other roofing materials.

Eternacaulk

As far as prep work, I would remove as much of the old material as possible. A heat gun will help speed removal of the old caulk. Clean as best you can with mild cleaners and limit the use of solvents as they can damage the base material. Plastic tools are safest to use and will help to keep you from cutting into the roofing. If you have to use something like a metal scrapper go easy so you don't add new unintended penetrations.

As mentioned lot of YouTube videos of how other owners work resealing a roof. Not technically demanding but there are techniques to help speed up the process. And "the bigger the glob the better the job" is not a best practice.

My advice would be to use Eternabond on the roof when possible.
Did you check Youtube for tips on applying caulk?

I wash the roof with dawn and water, rinse and allow it to dry. Then I remove the loose caulking, clean the area well with lacquer thinner and apply the new caulk over the old.
If you want to remove the old caulk, use a heat gun on low and a plastic scraper. Some use a multitool and have good results.,
Take your time, it's not difficult.
Dicor self leveling is an excellent choice for horizonal surfaces.