... Some jobs are best left to a professional. IMO, this is one of them. I'm sure there are 'tricks' and methods to do this. You could start your own Bathtub Reglazing Company if you want. In addition, besides the chemicals, there is special application equipment that's used.
No criticism - just my opinion. My best to ya and hope this helps.
Jay J -Moderator
PS: Depending, I think you can have this job done for between $200-500, tub only ...