My L4D Map

[Con]

1. Open Hammer
2. Open your level
3. File -> Export to .DXF
4. Twiddle thumbs while it does its thing (might take a while)
5. Import into 3DS/Maya/whatever
6. Model/Texture your railings/other junk
7. Export and place in level

I've never made props before, let alone destructible ones, so I went with making a brush railing with breakable glass.