Buttons,
Tools:
silicon grease
Soapy water
Fine point tweezers
Toothbrush
You say you removed the pushers therefore you know about the circlips. I use the same silicon car spray you use for the rubber gaskets on the doors and trunk. Spray some in a small cup.
Remove the pushers; clean them in soapy water.
Ensure they are straight and not bent.
Ensure the o rings are not cracked.
Rinse and dry the pushers.
Soak them in the silicon spray in the cup overnight. (This softens the o rings which have hardened over time)
Coat the pushers in silicon grease. Seiko makes some but the electronic store will have a toothpaste sized tube at a fraction of the cost.
Clean the pusher tubes.
Insure the tubes are not deformed (must be round). Use a fine pointed round awl to open or round the tube opening.
Insert silicon grease into the pusher tubes.
Insert and work the pushers in and out.
If that does not work then replace the o rings. Seiko or generic from someone like Borels. Use the case number which is the second set of four digits in conjunction with the movement number when requesting.
It is a good to replace the case gasket and battery gasket as well, but treat them the same way as the pushers vis-a-vis the silicon spray and grease.
Good luck.
Geoff