I use a silicone mold-release sometimes.  Works really good, but it's more expensive than wax, takes the same amount of time (need a couple coats plus dry time.)  I ended up going back to Partall release wax.   
  
PVA is only so-so in these applications, if that's what you meant.  More trouble than it's worth, for sure. 
  
 
  
Thanks 
  
The wires for the amp were planned from the git-go.   
  
You'll notice on the end  of the amp rack nearest the seat there is a few inches of space as it gradually curves down.  Wire channel!  And the amp is spaced up 3/8" so the signal cables run underneath it to plug in on the other side, and allow for a little extra cooling via convection. 
  
Wires down each side of the car are zip-tied about every 6", and loomed anywhere they need protection - under the hood, above the drivers feet.  The battery was re-grounded, and the amp was grounded to the floor below the back seat. 
  
I own Bobwires Audio