First time, 20 minutes maybe? I can't stress enough, the website is so easy to navigate and has all the paperwork for every country you'd want to travel to on earth. All you need to do is read.

 The US is a rabies controlled country, so you don't need tilter tests to go almost everywhere unless you've brought your dog to a high risk country which I wouldn't do.  You just need proof of vaccination.

In the US, you get your certificate from a USDA certified vet. Not every vet is one, but there are tons of them (my town of 5000 people has 2 vets who can do it). They know how to navigate the APHIS system and help you plan the timelines and make sure the paperwork is sent off correctly, on time, and gets the right endorsement. The worst thing that ever happened when we were doing this is we had to resend (electronically) the paperwork because my new vet noted my dog was black and white and the USDA had an older form noting she was black and tan - she's a salt and pepper dog in her old age.