Mannyrock...
Midwest's 'cork' roadbed is, and always has been, a mixture having some sort of rubber(-ized) material to bind the ground cork particles. This is what gives the product its flexibility.
As for the 'stink' fresh out of the box, that's good. It means the stuff still has good flexibility.
Back in my HO days I was given a boxed supply of old Midwest cork roadbed. Same stock number, etc.. But it didn't have the 'stink'. So when I tried bending it into sharper radii (22"R was necessary for my early HO layouts) the roadbed cracked, split, broke when bent. It had lost its mojo. The friend who gave it to me had stored it in his basement, humidity controlled. It was just.....old.....like me. (I tend to creak a lot, but haven't 'broken', yet!)
So, be careful for what you wish for.
OTOH, when I built my rather large basement O3R layout (Gargraves/Ross exclusively) I used Midwest O cork roadbed. Immediately after I laid it...before the track was fastened to it...I painted it gray. In fact there's about 3 shades of gray on the cork roadbed throughout. That's because I was cheap! I got my gray paint from Home Depot's "Oops!" paint offerings...tints that didn't turn out quite right, customer rejected, etc.. After all, I don't know whether you've noticed new-builds, fixer-uppers, and other decor efforts, but 'shades of gray' is not just a steamy novel title and series of TV movies!....it's one of the 'in' colors....exterior and interior. They call it "neutral". I call it model railroad handy!
Whatever. It gave the brown cork a reasonable short-term roadbed appearance, AND tended to stifle the stink.
Somewhere down the road...probably after most of the scenery is done...I may apply ballast over the track and roadbed. I'm one of those oddballs who lets gravity keep the ballast in place...no glue, no binder. I don't think that technique is very workable in smaller scales...HO, N..., but I've experimented leaving the ballast loose in O3R. It stays put well on a permanent layout. If a derailment or local maintenance task messes up the ballast, a small brush puts it nicely back in place. And someday...after I've dropped my fire...folks can simply put a clean filter in the vacuum, easily retrieve and re-use it, and have lots of clean track/switches to work with on future layouts.
Until then, the gray paint is nicely adequate.
As usual and always...FWIW. TEHO.
KD