We'll concentrate on the ap2 cars:
Take the side panel on the right hand side out, disconnect white round connector cable from autopilot unit and plug into that cable yourself (it's ethernet in disguise) using
a ready made cable or a pinout like this:
https://teslamotorsclub.com/tmc/attachments/20140222_164339-jpg.44438/ (alternative - buy diag unlock token for your vin on the dark internet, sorry, no pointers, that would save you the trouble of taking the right side panel out - connect to the cable under the CID then).
give yourself ip 192.168.90.103 and connect to 192.168.90.100 port 25956 (use telnet)
at the prompt enter: "install
http://someserver:someport/path/firmware.bin" - obviously replace the server/port and path to correct values on a server you control (always use the port even if it's 80 - e.g. use the url above or get your own server), then wait until transmission is done (monitor the transfer on the server side, the "this file is not served" error you would see is a distraction, ignore it) and quickly reconnect the white connector back at the autopilot. Wait until the yellow clock icon appears. Initiate install at your convenience.
pictures TBD.