This is difficult in some cases as with a lot of cars, you can hardly get your hands around the tip of the filter, let alone wiping off. I've just got into the habit of checking the filter once it's out now.I wipe away the excess oil to remove any dirt/oil/o-rings every time to do a service, without fail.
As far a sump plugs go, I don't take the pan away without replacing it first, so I've not had the problem of leaving it off.