Getting a vacuum cleaner in there wouldn't hurt really.
If getting oil down between the outer and inner parts of that column is required you might try cutting a cheap plastic funnel at the right point to be a firm fit over the outer;clean it up really well and then wrap self-amalgamating rubber tape round the stick to seal it fully and then just pour the oil into the funnel. Let gravity do its job. If the centre part needs to be pushed down then you can do it with any hammer handle or whatever.
Never had this apart so don't know what you are trying to do really.
Good luck mate.