No need to add FeCl3 occasionally. You need an oxidizer to get it started and initially get copper (II) in solution, but once you have a lot of copper in solution, the only replenishment you need is occasionally adding some concentrated hydrochloric acid.
So, you start with FeCl3, dissolved in hydrochloric acid. Equally well (or even better) is adding some H2O2 to hydrochloric acid.
To this, you add copper and that will dissolve and after that you keep the stuff in contact with air.
Each time you want to use it, just keep it in a container, with air contact several hours before you immerse the PCB. After use you can store it in a tightly closed container (it gives off corrosive fumes, so you want it isolated, when not in use) and a few hours before using it again, you leave it in contact with air again to absorb oxygen. No need for annoying bubbling sessions.