I've done that with Laurel Mountain Forge browning solution and it came out very nice on the Hodgepodge rifle. Go to their website and download the instructions for browning, it is in there. I made a tank from 4" schedule 40 PVC with a couple of end caps glued on, after cutting about 1/3 of the length away for a slot to put the barrel through. It's been holding up very well, much better than the cold bluing I've used before.
Even LMF browning takes time. The first 5 or 6 coats don't seem to do much but then it starts going faster. If you have polished the metal it will take longer, may not even work. It needs to be sanded to a matte finish on the bare metal if you want browning to go faster. Those first few coats start the rusting process which roughens up the surface so it can really take off. However, having the metal smoother does give a glossier final finish.
~Kees~