First time aluminum boat owner. Hull question.

Hi. I own a 20 foot Lifetimer. I keep it in saltwater year round. The hull is painted black from the water line and lower. I'm going to pull it and potentially paint the bottom. I can't seem to find a good resource after googling a lot, on step by step, simplest bottom painting method. Can I just touch up? Or do I have to clean with a chemical, sand, and paint? Do I only need to apply one product or several? How often should one bottom paint a boat that is left in the water, yearly?

First time boat owner so any help is appreciated, thanks.

You might want to read through this thread and see if it helps answer your question. https://www.tinboats.net/forum/viewtopic.php?f=3&t=28275&p=290385&hilit=fouling#p290385

if you can, take a picture of the bottom. It really depends on how bad of condition its in in my opinion. If its something your going to have for a long time, you may as well spend the time and money and do it right. Saltwater can reek HAVOC on aluminum boats. The first boat I ever got was USED in saltwater, not kept, and it had a bunch of tiny pinsize holes from oxidation. I used gluvit on the entire bottom and never had an issue with it.