There is always also the stroke practice of laying a small mouthed bottle sideways on a table at approximately pool table height, and stroking with your actual cue cleanly into the bottle opening
[why does that sound lurid lol]
It has been shown in studies that mental visualization practice can be very effective at helping with physical performance. Even basketball free-throws. For pool, all you need to look at is the jump in performance level by well-known pro players that have spent time in prison. Tony Chohan -- it may have played a role in the jump in his One Pocket game, and Dennis Hatch is another one. Going back, by accounts it sounds like Clem Metz may have kept his pool game strong that way. I have at least one local friend same thing. As I recall what they suggest is get yourself comfortable in a quiet place if possible and visualize with as much detail as possible, completely through each action along with the thought process. So study the table, select your shot, approach your shot deliberately and get down in your mind with a good bridge, stance and grip. See your angle and work through your aiming process exactly, whatever warm up strokes you normally do when you are shooting well, and visualize right through your final stroke and the cue ball taking off correctly and likewise the object ball, and finally both the cue ball and the object balls coming to rest where they were supposed to. Don't forget to stay down on your shot
My understanding is that even if you have zero physical practice available, mental practice helps, but it does work best when you are able to combine a mix of mental and physical practice. I would suggest if you have no table at all available, combine the mental practice with the bottle or some other basic physical stroke practice. There you have it -- a combination of mental and physical. Watch out, we are all going to come out stronger for this!!
I'm going to go out on a totally unscientific limb and say that One Pocket is especially a good discipline to practice this mental visualization, because so much of the game is already in the thought process, compared to other games.