How to detonate sticky bombs in GTA V for PC

According to the manual, there is no difference.

A and RB buttons are both mapped to the handbrake, so it's just for convenience.

Personally, I alternate between the two based on what I am doing.

Example:

When I want to change weapons, X, and make an immediate sharp turn, I would use A.

Otherwise, I would use RB (especially if I had to answer the phone).

Hope this helps!

I also bought it and the same happened to me. Although now after I've bought another property and they want me to do a mission for them a "P" pops up at their location. So I guess it's either bugged or it will appear later, my guess is on the first alternative.

(Edit) It seems like there is a third option; if you take too long they don't want your help anymore and send you another text "saying so". Check your phone for another text from your property.