Foster replaced Hart as Brum's No1 this season after deciding to leave Manchester United.
"The goalkeeping coach, I can't speak highly enough of Dave Watson," Hart told the Birmingham Mail.
"I worked closely with him. Every day means the world to him football-wise and he is going to do the same with Ben.
"He will really push him. Ben is a great 'keeper and it will be great for him to be a number one and you have seen in his early performances for Birmingham that he is going to do well."