Hoek will join the Reds alongside new manager Louis van Gaal and assistant coach Marcel Bout after completing his duties with the Netherlands at this summer’s World Cup.
The 57-year-old was van der Sar’s first goalkeeping at Ajax in the early 1990s and the Reds’ former no. 1 believes he’s a good appointment.
"He groomed me and helped me learn all the things I needed to know to be a successful footballer over a lot of years," van der Sar said.
"Like Louis van Gaal, he’s really exact with his exercises – they both put a lot of thought into them. He was one of the first guys I know who connected the goalkeepers with defenders and midfielders in terms of exercises.
"It wasn’t only about practising goalkicks as a keeper – he would think about the different situations you might yourself be in during a game and try to find exercises and drills for us that he would combine with the outfield players."
Hoek will be tasked with helping United’s Double Player of the Year David De Gea continue on his upward curve and van der Sar added: "He should be a great help for David.
"He used to work at Barcelona so he’ll speak Spanish, which will help, although I know David speaks good English now. I think they’ll be a good combination.