When I flew to Seattle, I didn't know that my license had expired. I was turned away at the security screening and told to go back to the ticket counter to get a "special" boarding pass. Given that I didn't know that you could actually fly with an expired license and no other government issued id I was happy enough to go get it. So I did and they gave me one and I looked at it and emblazoned on it was "SSSS" which I now know means Secondary Security Screening Selection. Oh this should be fun. It was fine. Not something I want to always take the time for, but in comparison to Heathrow or as I've heard Tel Aviv, it was quite painless.
They get a TSA employee of the same gender as you are, and carefully explain that they are going to do a "pat down" search. The employee carefully and lightly, in my experience, pats your arms, sides, hips, and down your legs, then switches over to your back. In the mean time, another employee goes through your carry on and swabs various places and places the swabs in a machine that is likely testing for explosives. As you might guess, they also swab your shoes.
The entire process, including going back to the ticket counter, took 15 minutes. My favorite part was when the TSA person says "you have been randomly selected." Um no, not in this case. coming back from Seattle, my experience was essentially identical.
I wasn't sure if they were going to be unhappy about my toothpaste being repackaged in a non - commercial container. No issue. No issue at all. Though I'm not sure I like taking the time before my airplane trips to prepare like I'm going on a camping trip, so in Seattle I bought toiletries to leave at my parents house.
Though I did renew my license when I returned.