Swabbing is good. Oil would be bad. A sabot does not need lubrication. The sabot itself is the lubrication. Getting it too slippery might effect the way it grips the rifling. Personally I would not do it.

Get some Windex and swab between shots. If the sabot/projectile is still too tight, go with a Harvester Crushed Rib or Harvester EZ load sabot.