I can only give ds1 an immediate reward , he doesn't understand anything else- so in the example below its the biscuit for going to the toilet. He has a thing at the moment about not changing t-shirts so today he was told "change then granny's car" and he got to go for a ride (obviously he was about to anyway but we just paired it with the t-shirt to make it a reward and to get him to allow us to changew him otherwise it would have been an all out physical scrap- which he would probably have won.)
In your sons case I suspect you could use a mixture "do x first then we'll get you ps" and also longer rewards- they have to be achievable though so if a whole day isn't achievable make it a half, if a half isn't make it an hour.
I'm trying to think of other recent examples he's big into pouring water everywhere at the moment but unless caught just before he does it (when a shout works) there isn't really anything I can do so I just ignore it. He threw some food yesterday (think he's copying someone at school) so I made him pick it up, then he threw it again so I physically escorted him to the bin (although he like putting things in the bin).
I'm getting help this holiday-18 hours a week funded by social services- I have a fantastic trainee SALT/ ex nanny who comes in 4 afternoons a week and looks after ds2 and ds3. That gives me a chance to take ds1 out somewhere which helps as his behaviour is worse when unoccupied (and he has almost zero ability to play although there has been some improvement recently).
Luckily my mum has this week off work so was around today- luckily as I have some achey bone headachey virus thing so it's been easier with more adults around. Just got to get ds3 off then its sit on the sofa time....
Did BIBIC give any behaviour management suggestions? Is his behaviour very impulsive, or does he just not understand?