I guess if you put the seal between layers of absorbant material (does anyone remember blotting paper?) and left it with a weight on it would draw some of the oil out.

I don’t think you can try to draw it out with a solvent like rubbing alcohol without damaging the leather.

If it’s not kicking like a mule and possibly damaging the gun I’d probably put 100 pellets through it and hope it settles down, but I’m lazy !