If you can remove the stock, just close the action...any water that comes out will do so slowly. But that's if you want the barrel sealed for soaking, you can also pull the breech plug and just keep pouring water down the barrel and swabbing etc. until you're done.
Plastic fouling from sabots can be a problem for some, but I never had an issue...just cleaned the barrel as usual between shooting sessions and I never noticed any problems.