Burnt ends: when to cube?

[cdcox]

My dad cooked a full brisket and we want to make burnt ends with the point. Brisket is already cooked.

So when you make burnt ends, do you cube the point before you put it back on the smoker or after you are 100% done with the smoker?

Do you think it would matter whether the final cooking was done on the grill or the smoker? Meat doesn't take up much smoke flavor after it's been cooked.