UPDATED 12/2017
I no longer recommend using Windex for cleaning the surface of an oil painting.
I’ve found that just gently wiping odorless mineral spirits on the surface with a makeup sponge, then rubbing with my palm or finger usually can “roll” the lint particles out of the surface. Then I wipe down with the makeup sponge to get rid of the debris, and then oil out the area I plan to paint over that day.
For best results do it on every dry layer throughout the whole painting process. Don’t paint over the dry linty surface with new wet paint.
Deeply embedded lint might need more aggressive sanding. If you need to sand down the surface, use 600-1500 grit wet/dry sandpaper, oil the surface with straight linseed oil or your medium, and start gently in a small area with just a fingertip wrapped in a small scarp of sandpaper. This will take up a lot of paint though and the area will require re-painting.
If you want more help feel free to join my online class, tons of resources there and I answer questions and give feedback if you work through my lessons in order:
www.sadievaleriatelier.net