Would it benefit working out my butt before surgery for bigger butt implants?

I don’t think exercise is going to make a big difference esp if you are already in good shape.
Most plastic surgeons don’t offer gluteal implants.
Why do you think that’s the case?
The majority of provides are happy to do just about any other procedure.
I suggest you think long and hard before considering gluteal implants.
Personally I’ve never met a patients who had long term quality outcomes from this procedure.
I’m not saying they don’t exist. I’ve just never met one and I’ve been a plastic surgeon for a few decades.
I have seen plenty of bad outcomes. I’ve never seen a good one.
This operation has a pretty atrocious track record of complications, undesirable side effects, and high revision rate.
I recommend people simply don’t have gluteal implants.
Quality fat grafting is usually the better option even if patients are not ideal candidates. That said delivering consistent quality liposuction and fat transfer is not at all easy or straightforward. In the hands of the right provider the procedure does work without the problem associated with gluteal implants.
It’s a free world.
Best,
Mats Hagström MD