Though I've never done this either,I've been planning for a few months,studying construction steps,trying to figure the best approach to assembly.
My approach would be to lay out all your parts carefully. Whatever you do,whether it be painting,cleaning out the steel bearing sockets,etc.,do 1 proceedure to all couplers,then move on to the next proceedure. I'm on prescription medications&assemble my medications for 2 weeks at a time&find this proceedure works well,dealing with 1 medication at a time,then moving on to the next 1,instead of changing back&forth. It's an assembly line procedure that works well for me.
Unlike you,I'm 56&the nerves aren't what they used to be,so I may have to go with preessembled couplers,though if I settle my nerves&get all my tools ready before hand,I think I can handle it. The bulk packs are great as far as the cost savings&the number of cars you can put on the track when finished. I can put 72 cars on the track at a time when assembling the SBE coupler bulk pack.
Did you know that there are now airlines on the market that couple magnetically? I've watched the U tube demo&they look really neat,expensive but neat.
Hope this helps.