I've been to Ukraine by bus last summer. Way out of Schengen:

• Slovak border control - the border control officer came to the bus, just checked the Slovak passports by looking at them and nodding, collected all the non-Slovak ones (including my bf's Czech), came back with them in about 20-30mins

• Ukrainian border control - they just put in the stamp with a date

Way back:

• Ukrainian border control - I got new stamp, yay!

• Slovak border control - a man collected all the passports, randomly chose a few Ukrainians for fingerprints, we waited for them for kinda long time. Then we went out of the bus and stood in line for bag checks. There were some people checking the bus meanwhile. When it was your turn for a check, you told your name to a woman who found your passport, swiped it and checked your face, while the other was looking through your stuff, mostly for cigarettes and alcohol. Then we boarded the bus again, they finally handed us our passports back and we could go.

Shit was Arstotzka like. The only thing that will be new now is probably just further database checks.