No, I haven't dropped the tank into POR15, it's almost impossible to get it off your hands when it gets on them, usually takes a week or so til it wares off, so be super careful with that stuff.
I coat the inside first , removing petcocks and taping over the holes, if the petcock is a double screw mount I lightly grease 2 sacrificial screws and send them into the taped holes. If it's a make thread mount for female petcock, remove petcock, cover the outlet with tape a couple times and then cover the tape while taping the threads to hold the seal and save the threads from getting this stuff on it. Carefully pour POR15 in a little at a time , then roll the tank to make sure that there is good coverage but not so much that it puddles, roll it often to ensure good even coverage when you think you have good coverage and it might be starting to dry, keep rolling it for a while longer and leave it set opening the petcock tape so any excess will drip out into a container of some sort ( it's really hard to get this crap off of any surface so be careful) give it a week to dry, then attack the outside of the tank with a fine bristle paint brush POR 15 smooths itself out allot and will drip like crazy so be careful.
I used this stuff on truck frames for years, the sun will dull it out fast so I clear coat and it stays nice for years.