Haven't done the Mexico dance in a while, so will let someone else answer. I do know you need to have the exit verified so that if you go back you can get a new TIP. If you don't do that part and the TIP is active for too long you can run into problems.
For the US, you will need a CBP user decal. You can apply online on the DTOPS system
. You have to give a mailing address, but you can buy online, give some mailing address, then go back online and get the decal number, you don't need to actually receive the decal (I haven't had a physical decal in years - they sit in the US at my mailing address).
Once you have a decal you can use the ROAM app, makes things dead easy. Put in the decal number and all crew information. If all crew have a "known traveler number" (Global Entry, Nexus, etc.) it will make things easier, but not required.
When arriving in US report arrival by ROAM. CBP will then contact you with requirements. One arrival we had a video chat by cell phone
where each crewmember had to show face and passport to CBP agent over video. Done. Another we simply got back an e-mail "you are cleared - proceed on your merry way".
One caution, CBP doesn't let you use an outdated ROAM app, so make sure you check for updates just before you leave Mexico.
[Edit] even with ROAM you will still need to plan your first US stop at a port of entry
just in case they want to see you in person.[/edit]