There are numerous ways to do this. The best is to let someone else do it and then you just drive and enjoy it! But you lose the chance t practice words that you usually use, avoid cuts and bruises and consuming too many cold ones out frustration!
I did mechanical first, springs, brakes, shocks etc.
On my ‘47 AD 3100 I didn’t want to do a frame off. I did the interior cab first-rust, floor sections etc. Then Interior pant.

Took off doors went through the mechanicals, then rust on door bottoms. Painted interior of doors. Took off back fenders reworked the fenders then paint. Next I did the removed box. Painted it. Clear coated the wood bed. Next did the front front fenders- removed of course. Took off the hood. Sanded, repaired the exterior cab and masked the interface the door jambs. I needed to replace the front and rear glass so I removed the glass. Prepped the window channels and taped them shut with paper. Didn’t remove the engine but needed to change the yellow firewall to original Cole- Mariner Blue. Learned a trick here to wrap aluminum foil over wires, cables etc. I carefully sprayed the cowl and it turned out great. The last part I sprayed was the hood. By the time I got to the hood the truck was assembled to that point.
Points made earlier are spot on. Tape carefully, pre-fit your parts before painting. Use masking tape on all edges when assembling panels to protect from scratches.

I found I could focus on single panels to do my best work. I have some photos if they would help you. Just pm me. Good luck.