I bought a Leitz CA2500 slide-projector a couple of years ago and have been using it quite happily apart from a couple of things:
1) there is a solenoid which should move when the slide-advance button is pressed, and it occasionally sticks;
2) the 'curtains' which close/open during slide changing are sometimes rather sluggish.
The first point should be relatively straightforward I think - the solenoid is easily accessible when the baseplate is removed - although I'm not sure what sort of lubrication I should use (if any?? There appears to be a small amount of corrosion on the solenoid's plunger).
The second point I think will need a bit of disassembly; but of course I don't want to just start taking it apart in case I can't get it back together again! I can't find a service manual online anywhere, whilst Leitz themselves would like me to ship the projector to them so that they can service it (at a cost of nearly £200 IIRC!)
Any corosion on the plunger of the solenoid should be removed. As a tool for it you could use a Dremmel or Proxxon with a blue polishing wheel.
No grease or lubricant should be applied.
For the "curtains" : take pic's ! Digi, if you have, is the easiest.
Degrease all the moving parts of it with Q-tips and some solvent: lighter fluid, petroleum or what ever.
DO NOT USE ACETONE as it desolves the plastic.
You realy have to clean that section thoroughly, hairs and dust can be removed with a small brush and a vacumcleaner.
Try if it works without grease first, if it does not run smoothly than apply a very thin coat of lithium based grease with a Q-tip or brush.
The curtains can be reached by removing the top (as if you have to replace the lamp) but having the bottom off gives you extra access to them.
No lube on the solenoid. If you clean it with lighter fluid though there is a very, very light residue that will provide lubrication, The linkage for the shutter may need a "poo-dab" of grease. A poo-dab is miniscule, a bit on a fondue stick is about right, if applied with a light touch.