You have just asked one of those questions that has a split number of votes.
First off, remember that your PC muscle is a MUSCLE! Although it is a quick healing muscle, it needs rest. Make sure to not overtrain it. A kegel routine anywhere from 5-10 minutes 3-4 times a week is plenty.
Now, with regards to becoming a "master" and controlling your ejaculations:
Firstly, this takes many years to master. Results will not happen overnight. Be prepared to have lots of practice sessions and lots of failed attempts. Becoming multi-orgasmic or having dry orgasms takes lots of dedication and focus.
Secondly, the answer of whether to squeeze your PC muscle or keep it relaxed is a tough question to answer. There are two groups. Group A found that when they strengthened their PC muscle, they became more sensitive, which led to them becoming premature ejaculators. They would squeeze their PC muscle as hard as possible when they felt as if they were going to cum, but in the end, it made them cum faster. As a result, these people started to do a reverse kegel (relaxing the PC muscle) when they felt they were going to ejaculate and it allowed them not to cum. Group B, on the other hand, tried to keep their PC muscle relaxed the entire time during intercourse/sex. As soon as they felt their were going to reach the point of no return, they would squeeze their PC muscle and hold it until the sensation of wanted to cum went away.
So, for some people, squeezing the PC muscle worked. For some, relaxing it worked.
If you read material on by Taoists on male multi-orgasms, they suggest that one squeezes the PC muscle (not relax it) if you want to prevent ejaculation. But, you must keep in mind that this method doesn't work on its own. Belly breathing, sexual coitus techniques or even the "Million Dollar Spot" are all ways to also help prevent ejaculation and help one become multi-orgasmic.
My suggestion to you is to pick up a copy of The Multi-Ogasmic Man.
Amazon.com: The Multi-Orgasmic Man: Sexual Secrets Every Man Should Know: Books: Mantak Chia,Douglas Abrams After reading this book, doing the exercises and lots and lots of practice, you should be able to attain your goal.
Personally, I have chosen to leave this part of my relationship with my penis for AFTER I have attained my PE goals. A man's relationship with his penis lasts his entire life. First, I plan to increase the size of my penis. Second, I plan to cement the size of my penis. Third, I plan to ensure that my penis remains healthy during Step 1 and Step 2. Finally, I plan to become Multi-Orgasmic. I think the last one is the hardest, but most fulfilling, even more than PE and attaining a goal of 8 x 6. What's the point in having a big dick if you can't use it, right?
Good luck luismastro.