The irritation problem (with the flaking, itching, etc.) is a major problem for me as well.
I've been on both proscar and minox for about 8 months now. Started off with 2% liquid and then a month later, the doc told me to try the 5% (liquid). It gave me massive flaking problems, to the point that 2 months later the doc told me to go back down to the 2%.
The flaking problem still persists and it's a huge hassle.
They don't sell the foam in this part of the world (I live in the UAE), and it's not easy to find PPG free stuff around here. I've been thinking of ordering the PPG free liquid from Dr. Lee's website.
Perhaps that might resolve your (and hopefully mine) flaking problem?