I cut a piece of rubber tubing so that it fits over the nipple and is long enogh to cushion the hammer, then I can dry fire with no damage.

That's what I do. I do the same thing for long-term storage as well.

I would not dry fire an inline. To releave the firing pin spring tension, hold the trigger back as you close and turn the bolt. This will let the pin move forward slowly.
I dry fire sidelocks when working on them by putting a piece of rubber hose like vacuum line or small fuel line on the nipple. It has to stick up higher then the end of the nipple so the hammer can't hit metal.

my answer is just the same as triple 7 use a cap or primer which is what i do when i shoot the first shot. if there is any oil left in the barrel one or two of the primers will clean it out really well
rob k

I have several sidelocks that have double-set triggers. I "dry-fire" these by setting the trigger, then it snaps when I "fire" it. The hammer never moves, but I can "call" the shot by noting where the sights were pointing when it went "click"!! This is one advantage of a sidelock over an in-line!!