I was wondering how fx artist deal with blowing up things like cars, fridges, buildings.
Do you animate it by hand (or get someone in animation to do it) or do you run it trough some kind of physics animation software?
I’m using UE4 and they do have a destructible mesh tool. But it makes everything blow up like rock. A car for example would have the hood blow off, the doors and wheels blow out etc. how do you explode something like a car ?
Something specific for a car I would take a look at this Car Destruction in Unreal Engine 4 on Vimeo , the creator shares his project.
As for buildings etc, these are usually preanimated / simulated and played back inside the engine, especially if it needs to be art directed to fall a certain way. I personally do all my presimulated destruct sequences in Houdini and import them via fbx or recently alembic, keep in mind , you dont want to go crazy with the amount of data that is being streamed, usually these sequences can be very cpu heavy.
The UE4 destructible technique works for smaller objects, doodads etc that you need destroyed. I havent used it too much but its definitely not something that I would try to art up an entire destruction sequence with.
I have been animating the components of my car blowing up in Maya (5 pieces) and then importing into UE. But I just cant get that realistic physics feel. So I was wondering if I was to take the hood of the car turn it into a physics object then at the point of the explosion apply some kind of radial force to it. This should work, right?
Yes, animating the main bigger components and then “activating” or simply hooking up your interactive pieces to it via hinges and blowing them off at the right time should work. I think for this though youll need to add some certain hook locations on your animated/simulated mesh, again not entirely sure , but give it a shot 
For structures, I used pre-baked animation made via RayFire call the animation with some trigger and hide any problem with particule.