Baby powder...apply some onto a cloth and wipe the surfaces of both the D-shaped seals as well as the sweep seals that rub against the sides of the slides. Then wipe again with a cloth without powder to remove the excess residue.
Been doing this about every 3 months or sooner if I notice any sticking/squeaking when operating the slides
I use silicone on everything. I haven't had any problems up to this point.
Dave, silicon is also a very common method of lubricating the rubber seals, if you use this method it is also advisable to wipe down the seals with a clean cloth to remove any excess. After treatment all seals should be dry.