Not sure if this will help but I started training DD who has just turned 3, a week and a half ago. The first day was a bit of a disaster and she went through 8 pairs of pants. On the 2nd day, after MN advice I tried her without pants and she has been doing really well since. I think in pants she's using them as nappies or simply sitting on the potty without taking them off (I'm afraid I've never been able to 'catch' her doing it so I'm not sure!) Also the 2nd day saw us introducing rewards for weeing (chocolate buttons/magic stars) and a bigger one for poo (Freddo Frog - luckily she's a once-a-day girl!). Might DS be open to a bit of bribery?
Before properly starting to train, we've had a potty in the bathroom for several months and DD would often quite happily use it and ask to use it (for wee and poo) and after seeing an older cousin on the toilet recently, decided she'd like to sit on the trainer seat too (despite screaming blue murder previously). I thought the transition to no nappies would be a doddle especially as she was taking her nappy off (and all her clothes but that's another story) a lot over the past few months.
We now have to try and re-introduce pants and I'm not sure how!