Got FP done in Phoenix.
I went in Today (Wed) at 10.30. The security officer asked what am I there for. I said FP. Then he asked for FP notice and said that my appointment is next month. I said I am going out. Then he said "ya ya". He asked for ID, I gave EAD. Looked at it and game me a pad, a form, a wait number, put my EAD in the pad clip and asked me to fill the form. They called my number, I went in, the lady verified info on form, and asked me to sit in a chair. After 5 minutes of sitting they called, a lady came and took me to the FP center.
FP machine is completely electronic. As soon as she scanned the bar code on FP notice, all the info popped up. She verified the info and then sprayed my hand with some water. Then she put some windex on a thick sheet of paper and wiped the "glass" area on the machine where we are supposed to put our fingers.
The she started taking FP for both hands, completely guided by the FP machine. The machine immediately rejects a scan if it does not like it so that the operator does it again.
After taking all prints, a supervisor came to check if all the scans are proper. She zoomed each scan and verified each one separately. Then she made me take re-scan of my little finger. Then she checked the info.
Note: you have the option of changing your address here.
Then the lady signed the form I filled up and gave it back to me. She kept the FP notice with her.
From the time I entered, it took about 20-25 minutes to come out. The real FP process took about 10 min.
Also there are double verification of scans, so the scope for error or bad fingerprints is extremely low. There is no ink involved anywhere.
Hope this helps.
Good luck to you!