A big problem, especially with an older glider is getting to moving parts that you can't see, and certainly not reach with a needle and syringe. I've spent many trials making a PIK-20B's controls operate smoothly. Bearings deep inside the wings and tail were intended to be "permanently lubricated", but that permanence was intended for perhaps a decade, not four.

My current solution is to run a small plastic tube along a bendable but otherwise rigid long rod along with a cheap USB endoscope, both attached at the end of the rod. This allows seeing and reaching several meters into structures to drip lubricant on redirects, rollers, and belcranks far inside.

I use LPS-2, as it lasts for a year on most moving contacts. Flap hinges seem to dry out faster so they need a second application mid season.