I was thinking of something along this line.  The pump screws onto a 38MM neck which, I think, is the size of a standard gallon bottle.  They sell them for quart and other size bottles as well.  The pump delivers one ounce per squirt and the pump can be locked down when not in use.  If you attached a short tube to the end of the outlet of the pump and had a convenient way to plug the hose when not in use to prevent leakage…

 

I envision setting the jug of oil on the wing by the fuel inlet, remove the tube seal, drop the tube into the fuel tank, pump, pump, pump, however many squirts you needed, lock the pump down at the end of the last pump, replace the tube seal, pump gas, go to the other wing, repeat, set the jug back into your carrying receptacle, go fly!

 

It might be a good idea to have the tube sealing cap permanently attached to the end of the tube so that even I could not accidently drop it into the fuel tank!  Or I guess you could have a small catch bottle attached to the side of the jug to insert the end of the tube into when not in use and not have a sealing cap for the tube.

 

http://www.usplastic.com/catalog/item.aspx?itemid=45403

 

 

Bill