I found rewards worked really well with my oldest (if he went one day he got a sticker, if he went a week, he got a toy, 2 weeks another toy, 3 weeks, another toy and by the 4th week he got a really nice
Lego set since that's what he is into). Once we started training him I want to say it took us a good month before he would go completely dry during the day and night.
My daughter basically trained in 3 days (if that). She started Preschool on her 3rd birthday and came home dry wanting to use the potty. Found out she had used the potty at school too. Then she wanted to do it herself but needed help putting her diaper back on and didn't like that so I put her in pull ups for a week (I should have just went to panties because she never wet them!!) She was sooo easy I basically didn't have to do anything to train her. She saw all the other kids going and I think she basically thought I want to do that and she did. Haven't had a single accident with her (expect for once at DL but that was Daddies fault, he didn't listen to her when she said she had to potty).
Have any questions we're all here to help. We did the timer thing with my oldest too. Where I'd set a timer for every 10 mins and then extend it 10 mins as I learned how long he could hold it for. Also made him go potty after every meal and before and after bed. Hope I'm not giving to much info but I found it frustrating to but tried to stay calm about it all because I found if I stressed about it he'd hide when it was time to go. Good luck!
Thanks! Sofia has become a favorite in our house lately and this was her reward for no more crying at school.