New to the MalibuCrew….how do I determine my shaft size and prop size that came with the boat?

Random orbitals are nearly useless on heavy oxidation.  You want a rotary or at least a gear-driven orbital.  Then maybe use the random orbital to take out any swirls/holograms left by the rotary.  

I'm gonna try to tackle some heavy oxidation too. Does this cheap buffer look like it would do the job? I'm thinking buying extra wool pads, etc. and whatever cutting compound is on sale.

Cheap Amazon Buffer

Well, after looking around I found this orbital buffer on a shelf. Not variable speed. 10". Useable with the right pad to remove oxidation and then seal?

That’s kind of where I’m at with the coatings too.  I started buffing on my Malibu yesterday and I definitely need to rethink my approach.  The blue didn’t respond to a wool pad and any amount of polish on a DA, so I may need a small rotary for that.  Also had a point where I wanted to throw up.  I took a 6.5” wool and light polish to where the old reg numbers were and evidently the gelcoat was thin there because I ended up with some yellowish spots 🤮.  So now I will need to plan on fixing that next fall. 

But wait; there's more (and probably many beyond this):

https://www.masterlineusa.com/

It's all in how you hold your mouth, apparently ☺