Best way to remove bottom paint ?

[abl1111]

Need the best, most cost-effective way to remove bottom paint - professional and DIY options.

Bought my '75 SC with red bottom paint 9 years ago. I sanded and faired it the best I could after a (12) month resto, re-painted w/ a nice, $$$, black ablative paint. I have been fighting that red paint ever since.

When I roll new paint on after scrubbing loose the winters 'oxidized' paint w/ a 3M 'doodlepad', large flakes of paint come off on the roller - right down to the that red paint !

So, if you have 'been there, done that' let me know...

Thx