I seem to recall a (successful) emergency landing in Scandinavia in the 1980s on an MD80 (?) after a serious smoke in the cockpit incident.
Biggest problems were communications between the two crew on masks, but also the density of the smoke. FO found it very difficult to read the checklist even with the aid of torch and holding it close up. At one point he dropped it, which didn't help.
Another issue was smoke particles sticking to the PFD making it very difficult to see. The Capt had to keep wiping the particles off, using his hands but still had to use a torch.
Somewhere in SAS there's a good video reconstruction of this and an interview with the crew.
This was in daytime, so you can see the density of the smoke alone can be a real hazard.
BEX