When I use the petal dust the flower comes out real splotchy. I cannot get a nice even coat. I hope I describe this well enough. Any hints? Thanks.

The petal dust won't stick to grease spots.

Try to use cornstarch for rolling with, and make sure your tools have been washed well to get rid of the last traces of crisco.

Yah, what she ^^^ said.
Any grease spots on the fondant/gp will cause what you describe.
Are you using a good, dry brush? Dipping it into the dry dust and tapping it off before applying? Should work just fine if there is no grease involved.

I blend my dusts on a tissue , with some cornflower before applying, I don't get streaks. I don't use anything to roll out my flowerpaste with , just my non stick flower board.

I put a little in the lid then dab up and down in it with the brush to break up the tiny lumps, tap off the excess. Sometimes I will lightly dust the same color as the gumpaste on first for a base coat then build the required color on top. Happy dusting.

I was also told that you need to use a natural hair brush, the dusts won't work very well with nylon brushes.