I started with my DS when he was 2 yrs old,and he didn't have a clue.We spent weeks with 8 changes of clothes daily,and I got to the stage where my frustration was making me cross with him,which was against every "rule" of toileting,and every principle I had!
A friend of mine said STOP,and start again later.He's still young,and not starting school yet.
Even with your son you probably feel "pressurised" to get this done before school/playgroup etc. but I have learnt (the hard way) that when they are ready they are ready and will do it in 3 days.
So IME I would abandon it,put him into pull-ups or feel and learn etc. and leave it a month or so.Take your cues from him,if he wants to sit on a potty or use the toilet go with it,if he uses his nappy then fine.
Be relaxed with it, and restart it again when he gives you cues.You have already planted the seed,he'll probably get it really quick on second attempt.
It'll also take the pressure off you for a while,its alot to do with a young baby.
I applied this new found logic with my DD's,they let me know when they were ready,DD1 at 2.5yrs and DD2 at 21 mths.(Girls do seem quicker)