On deadline day, Coleman brought in Cardiff City goalkeeper Lee Camp, Liverpool midfielder Ovie Ejaria and Middlesbrough forward Ashley Fletcher as he looked to strengthen the club's bid to avoid relegation from the Championship.
However, the former Wales boss - taking part in his first British transfer window since 2010 - revealed that he had not enjoyed the process of trying to sign new players.
At a press conference, the 47-year-old said: "It was shocking, if I'm honest. It was brutal. I'm glad it's done. It's turned out good for us, we've injected some new faces, but I have forgotten what a farce it all is.
"You start remembering how it was where you can't trust anybody, you get told loads of lies, and to get any kind of a deal across the line is so tough."
Sunderland currently sit in 23rd place in the Championship table, just one point adrift of safety.