Hello! Part time transfer here.
To start i know this thread might be closed, but this is for anyone browsing this thread going into a transfer.
The process was simple as filling out a piece of paper and running around the facility to find the right person to sign the paper. The document HR provides on myHR pretty much tells you everything you need to complete the transfer as a part time employee, and what requirments they have.
From my experience though, i ran into alot of problems regarding the Union. You might transfer as a UPS employee, but your local union does not transfer with you, meaning you might have to apply to the local union and pay your 200 initiation fee again (Bull

, i know) and your paychecks might be screwed up for a week or two, though that one really depends on how well they handle the transfer. I am currently still paying a 5 dollar tax on the state i used to work in, but im getting that worked out here soon. Applying to this new union will also cause me to drop my pay down from my original pay, which is a big problem for me, which i am going to a meeting to dispute soon.
TL;DR it looks simple on paper, but we have a saying here; "Its UPS, things never go smoothly." You might run into a few problems and bumbs on your way so here are the things i wished i did before transfering, or things that have helped me when i did transfer.
Ask your managers, HR rep, and Union reps any questions you might have, and keep any documents or copies of documents you have accumulated during your transfer. Keep your old building managers number handy incase you need to reach him, and get to know your managers and union reps at your new building.
Hope this helps someone!