I too use the seal spray designed for the slide outs. After making sure the seals are free of dirt, you simply shake the can, spray the seal front and back, allow the foam to penetrate for a minute, then wipe the excess with a towel. That's it. You will notice the seals will be more pliable and have a glossy slick appearance, aiding in the travel of the slide across the seal.
*Current: 2005 Ford F350 Crew Cab Dually 6.0 diesel 4x4*
*Retired: 1987 F350 Crew Cab Dually 6.9 turbo diesel
2007 Forest River WildCat 32QBBS