I've been loading up the poly bullets from Palmetto and here are my steps:

1.) Use the Lee Universal Case Expanding to flare the case mouth just enough to hold the bullet upright before seating.
2.) Seat the bullet and check to make sure the coating didn't strip off. If some did, flare the case a little more. I'm using a COAL around 1.950.
3.) Use the Lee Factory Crimp Die to to take the flare off. You'll want a really light crimp. Too much crimp and the coating will strip off as the bullet exits the case.
4.) Drop in a Sheridan gauge to make sure it "chambers".

If I'm setting (or resetting) up the dies I'll make a dummy round or two and pull the bullet out afterwards to see if any coating strips off.