Ok. So the architect called for a 26' douglas fir beam rough hewed into
a shallow arch as an accent piece for our front porch. About 22" deep
at the ends arching down to ~10" in the middle. About 6" across.
Impossible to find in the east so we put in an LVL and I figured I'd
veneer it with two by spruce all glued up to look like a one piece
beam. Lots of work later, it's almost done. Problem is, it looks like
veneered glued up spruce. So I bought a steel brush for my drill and I
tried roughening it with the brush. Sort of works but lots of work.
Then I thought, ok I'll wet it down with a concentrated brightening
agent and let it sit for a while eating away at the wood - then use the
brush. Or perhaps rent an angle grinder and get one of those wood
carving attachments. But I think that maybe those cutters cut too
smoothly so it won't have the desired effect.

So I'm asking for advice. What is the most effective method of turning
milled lumber back into rough cut?

thanks,
Doug