Correct me if I'm wrong.
A PC shoots with a GRG at a BTR-70 and hits and it penetrates.
1) I make a roll on the Component damage table for the direct damage. One or more components is destroyed/damaged. If the "component" is a person, it is important to know whether the damage is enough for a critical hit.
2) Then I roll for the explosive effect (2D8). This damage effects all inside the vehicle. At the same time, IF I've rolled Fuel on Component damage, the fuel tank catches fire.
Remember to make CUF checks to see if the crew are forced to bail but. The rules say to do this for each individual occupant but I would suggest instead to make a single roll for the entire crew - i.e. they all stay inside or they all bail out.
Remember to check for ammunition explosions if you penetrate the Ammunition component.
Cargo hits are a bit problematic. The rules say everything has REL 5 unless otherwise stated but I would suggest using some common sense here. Maybe if some food is hit it only takes 2 damage to destroy it.