In the just for what it's worth column, I recently tried Eastwood's
rust encapsulating paint after getting rave reviews from three different guys I know who fix up old cars.
Its formulation appears to be relatively similar (just like POR,-15, any specks won't wash off the skin). I liked it for three reasons--the paint does not need UV protection in any color, the paint is also available in spray cans (Balgryn, I never
want to clean this out of a sprayer, you are brave!
), and finally, even with regular shipping, I got supplies from them the day after ordering (nb they are somewhere in PA, I am in the DC area).
Prep is the same--brush off loose rust, a hose down is probably also good if there's lots of loose stuff. Then just paint away.
I think that both are very good paints, I just find the Eastwood product a tiny bit better. I wouldn't throw out any POR-15, but you may want to check it out see if it might be more suited to your use if you haven't already started buying paint.