We owned a 40' steel sailboat for a bunch of years, and did our own maintenance. I know first hand what it takes to try to remove 30 years worth of bottom paint and various coatings.
I have worked in the marine industry for several decades, currently for an aluminum boat builder. We have several sand blasters, several wet blasters, and one of the stupidly expensive 40,000+PSI water jet blasters.
My best advice would be to shop around and pay someone to do this job, it is the best money you will spend on a metal hull.
If you insist on doing it cheap, rent several vacuum sanders, buy several cases of grinding discs, and hire a couple guys from the local Home Depot. You might get the hull done before word gets around and the Home Depot guys start refusing to work for you.
Anyone that suggests buying some cheap equipment, watching a video, and doing it yourself, has obviously not taken their own advice.
My 2 cents.