Underwear to potty train your child

Potty training can be a difficult task. I had a hard time training my son. One of the things that helped me was buying him "big boy" underwear. I told him that only big boys wore cool underwear. I knew that he liked Mickey Mouse so I bought him some Mickey Mouse underwear. I also made sure to time it took him to go pee in his diapers and estimated that time and sat him on the toilet. It took a few accidents but he finally got the hang of it.

I am starting to potty train the twins and I am hoping that the process is as easy as it was for my other son. I again bought cute underwear as an incentive and I have been making sure to take them to the bathroom quite often. I keep hoping that they will catch on soon. I hope I dont have to keep buying diapers because it can be a bit expensive. How long did it take for you to potty train your child?