This is how smoked hella headlights for e30 are made.
Here is a templete that you can print out and use to cut out 1,5-2mm thick aluminum plate or a rust free metal of your choice.
Then sand down the metal and paint with heat resistant matt black.
I’m considering to have few of these made and sell them here, depends on the interest in them. If you would like to buy a set, please e mail me at einar at bmw-e30.net
Best way to do this is to disasemble your headlights, take everything off. Put the ellipsoids into a cold oven and heat it up around 160° celcius (350°f) and bake them for 40-45 minutes. Then the oem glue should be soft enough so you can pry out the front lens.
Low beam is very easy, just sand down the mirror and paint with matt black.
High beam is a little bit more trickyYou need make 4 holes for the cross. I used dremel from the rear side and slotted the holes so the cross fitted perfectly
Apply some sealant and let it dry, preferably with something heavy on top.
And your all done