I use the Milich filter adapter and Cornerfix, and either the 15mm CV finder or the WATE finder. The WATE finder is nice because it has a bubble level, and the 16mm frame lines are very accurate but it's a lump and makes no sense unless you have the WATE as well. The 15CV finder isn't quite as accurate, and without frame lines you have to make sure your eye is in the correct location if you want accuracy but it's the logical choice otherwise. Another possibility is the Zeiss finder for the 16mm Hologon. They're not too expensive and they also come with a bubble level. I got one years ago as an alternate for another lens. The only problem is that it shows less than the 12mm lens covers on the M8, whereas the 15CV is more accurate once you know where to place your eye.
Before I had the Milich adapter I used the CV 77mm filter adapter, but it's huge and a pain; also you have to put something back of the cutout or you'll get reflections through the back.
If you don't have or want to use Cornerfix leave the filter off; IR contamination will be a problem that you will have to deal with (to whatever extent in post production), but will never give the quality of filter use with Cornerfix.
I got the lens right after it became available, and have been delighted with it on film and digital.
Henning