Can I just use a tub refinishing kit and refinish my own tub?

Yes, but it will not look nice nor will it last. Unfortunately the do-it-yourself tub refinishing kits sold online or at Home Depot or Lowes do not provide the proper adhesion preparation components to prevent the inferior epoxy finish from peeling off the tub within days. Since the kits use a roller to apply the finish, the tub will have roller streaks no matter how much the kit’s instructions say it will level after applying it. The worst part is that to have the tub reglazed professionally will cost 60% more than if the tub was reglazed professionally the first time as the epoxy finish needs to be stripped off for the tub to be reglazed properly.