I've gone as far as using HOK reducers with PPG clears without a problem. I know most would recommend against it, but in a pinch it worked for me.
As far as the Dry Pearl, you shouldn't have any problems at all. I've used both HOK and PPG dry pearls mixed with the others clears and haven't had a problem. I believe the HOK tech manual may even say it's ok to mix dry products.
Good Luck - Stretch