I don't pretreat Platine. Once Bostick and Sullivan stopped carrying Crane's Platinotype I tried a number of papers but have worked best with Platine. It has a nice natural color, coats easily and has good wet strength. I found that when using a puddle pusher it is best to have a piece of matte board under the paper rather than having the paper directly on a hard surface. I also let the emulsion soak in for about five minutes before drying it.
Jeff- are you doing palladium, platinum/palladium blend, or pure platinum prints?