T.D.
ok, please don't feel bad, I have twin 3 1/2 year olds that have just started Pre-k also. They hve trouble transitioning as well.
However, one strategy that has worked is for his teachers to reward him when he is good. Each school uses different rewards. Mine uses ticketts that earn them something in a treasure box. "Catch them being good more often" is really the best motto for any kid. Then they will be more apt to continue that good behavior.
There are many reasons why he is hitting and fussing. ( I teach children with behavior probs, so I have encountered this often) One main reason is for atttention. He might miss you and crave that missing att. from mom and has found that they come up to him etc when he acts out. Even if it is negative attention, it is still attention. They might have to ignore behavior, by no eye contact when he is throwing a fit or refusing to clean up. They can just physically prompt him to clean and go to next activity with no verbals. Then walk away without saying anything. (not giving any attention to the behavior). Then when he does it quietly next time, reward, praise, etc.
At home you can use letter magnets on fridge. Use the letters of his name. Everytime he gets a good report from school he adds a letter to spell his name. If he gets a negative report, he gets no letter. (This way it is visual and he can keep track too). At end of week if his name is spelled he earns something that he picked out to work for. (trip to library, toy from dollar store, etc) Has to be highly motivating. "Catch him being good" and reward with praise, an m&m, etc. Don't wait until he is bad to start implementing praise. B/c then he will think if I act out, mom will offer me a treat for me to be good. don't do that. kids pick up fast.
good luck. (my team at school uses this strategy. The team consists of Speech Path, and school Psychologists. So I really know they know what they are talking about.) Be consistent.