My daughter was a child care provider and several parents could not potty train their children especially little boys.  But my daughter potty trained them within a week. NO Problem.  She simply made a game out of it in the beginning.  She kept a small cup of Fruit Loops in a cup on the sink.  And dropped a few inthe toilet.  Then had the boys 'aim' to see how many they could hit'  They were so happy, it taught them control in the process so the rest of the  bathroom wasn't sprayed.  You can do it with girls also but at least it sort of 'forces' them to push instead of sitting around for too long doing nothing.

Good Luck I know it will help.