| Do you think Bondo will look anything like wood? I could sprinkle
| coarse sawdust on it before it dries, but I think that won't stick for
| long. Or is it just supposed to be a neutral color filler?
|

Bondo's not going to be much use with old wood.
You could treat it with sealer first, but that's really
for cases where you have a punky *section*. In your
case the whole post is old. I would expect water to
start seeping around the bondo patch before long.