IMHO, there's no point in doing that. POR is a rust encapsulator, as mentioned. It's sole purpose is to seal a rusty surface. If you remove the rust, there's no point in using the product. There are many other products designed to go over bare metal that will work easier and better than POR, in that application.

 

I kinda disagree with that there is no sense if the frame is sand blasted. Por 15 has the reputation as being a powder coating in a can.
I sandblasted my frame and some other parts and you can take a hammer to this stuff and all it does is go a whitish color from the impact and when wiped all that maybe there is the intent from that impact (no pealing, flaking etc.). I used no cleaner or anything after sandblasting my frame and the fact it self levels with a brush is nice too.
Just my 2 cents!

 

I can't speak about POR-15 because I've never used it but can say with certainty that body work is a pain in the a$$. Just when you think you have done a spendid job and you spray some primer on your handy work you find out in a quick hurry that you're just an amature.

 

That's what I had heard too, but I've never used POR15, so I wasn't sure.