Red,

"grabbed a beer"
Always a good idea.

"Put some light oil on the coontact surfaces"
That is a good idea IF you understand that the contact surfaces are the center rod of the piston to the small center hole of the dash pot. As I understand it, the dash pot to piston are not supposed to touch, so they do not require oil and in fact should not have it as the oil will interfere with the operation.

The normal procedure is to clean the piston, clean the inside of the dash pot, and then check for similar drop times while they are in the installed orientation. Only after this check should any abrasive be used on the large diameter of the piston, and then only on the slow one to match it to the fast one. Even before abusing the piston with abrasive, you should try switching the pistons and dash pots to see if that brings them into balance with respect to drop time. Sometimes switching (even though it should not normally be done) will create a match, and in my opinion is better than removing metal.

Charley