The rolling stool with a swivel seat is a good suggestion, it can relieve the legs even for a few moments whilst processing. Can the bench height be altered to something more comfortable? I think that paterson made a tall focus finder so there is less necessity to bend down so far to focus and I believe that enlargers such as De Vere had/have front control wheels just under and in front of the baseboard to control the height and focus - no need to raise the arms high to focus etc. Would a vertical print processor be easier to use than trays spread out? Just a few random thoughts, but one nice wet print must be better that a hundred digis!