check on cruisers forum if you want, Minaret has some great posts on bottom paint removal. He recommends using a big grinder.
No matter what you do, please follow the tenting guidelines correctly. There is nothing more frustrating than people open sanding scraping and grinding bottom paint and getting it all over everyone and everything else in the yard. DIY'ers are becoming more and more restricted because of complaints over stuff like that.
Instead of the preservation tape that Minaret recommends(costs a fortune).
We use tuck tape on the clear plastic(NOT on the hull.) and stick that to the top of some red poly tape that leaves no residue on the hull.
I have not used the big grinders myself, we stick to the traditional scrape+sanding.
I third the scraper type Tommays suggests, with the caveat that we change blades regularly, they can be sharpened, just lay the carbide flat on a piece of wet and dry and make small circles. Get 2-3 sharpenings before they are not cost effective to sharpen.
For sanding, a palm sander with a vac hose attached works well. A lot of yard guys will use dewalt or bosch then duct tape the hose onto the fitting for the dust bag.
If you've got cash lying around, or like woodworking etc. The Mirka 6" sander coupled with a Festool vacuum is the coolest thing ever. Their papers are a mesh, and they run a separate DC power supply so the tool is as light as an air powered sander, then the Festool is hepa filtered with disposable bags for ease of cleanup.
as a bonus, the suction on any sander helps reduce the weight on your wrists when you're sanding on your back.
Here's a recent scrape and sand.
You can see the scraped surface towards the stern, gelcoat should be visible.
Then sanding takes it down the rest of the way as you can see towards the bow.
This one was brutal, the owner had alternating layers of hard and ablative, so it was impossible to get a clean scrape, most scrapes were 1/4" or less per pass.