Potty Training - the beginning

I have been trying to potty train my boys for a while now.  They understand what the potty is, and what you are supposed to do on it.  Lately I resorted to putting underwear on them and asking if they need to use the potty every couple minutes.  They did not like the feeling of peeing or pooping in the underwear, so they were forced to tell me right away.  Before with the diapers they would just keep on playing even though their diapers was really stinky.  I found the best results were from giving the boys stickers every time they peed or pooped.  Currently Ajay is up to 8 stickers, and Maddox only has one.  Maddox is definitely the stubborn one.  I know they will learn eventually, right now it feels like a long time.