Two IDs (in my state, which is Red): log into a website with Social Security Number and confirm other personal info, like birth date, address, location, phone &c, confirm via text to phone, and add driver's license number. Ballot is mailed to home address in the US. Friend sends ballot to you in the other country. You fill in the ballot with a pencil or black pen, sign it, put it in an envelope and sign on its seal, and put that in the postal envelope and sign on that seal, and mail it directly to the State office managing votes. The state sends by email a confirmation when they receive the mail-in ballot. If the signature and date are not appropriate on the ballot, or the on the envelope in which it goes, or on the postal envelope on which that nvelope goes, the ballot will be rejected (and indeed many were).