Homesote work very well for the building surface as far as pins go.
As far as the bench I would go with the hollow core door, rather than the particle board, it will not sag as much.
I use a balsa building board on my bench for building on. But in the past have used homesote or the tile idea.
The garage makes a nice work space as long as you can keep the stupid cars out of the way...
Be careful about opening the garage door when it is windy out though...
Don't ask why I mention that one...
I was picking up balsa and plans for a day and a half.