My favorite is a spot hogg rheostat that is a infinite adjust, because in the off position you can turn one way to go bright and the other way to go dim. You want the dimmest possible setting for shooting in near dark. I have done the sharpie trick and for me this was enough to dim new batteries down enough.
Another trick is to play with the fibers and get them blocked off from the light source. I don't like all 5 of my sight pins to be lit up by the rheostat, the only one I want to see is the 20 yd pin. So I take a piece of black tape and go around the 4 I don't want to see right where the rheostat light hits them. I leave the 20 yard pin visible to the light source.
The g-5 rheostats about 7 years ago looked awesome but within weeks they all failed and had internal issues, for me the spot hogg lights always dealt well with weather and stuff and I have some from back to 2007 that still work good. I have some spot hogg ones that have 5 settings and they are more easy to find, the infinite adjust good one is hard to find. You might call them and see if they have them and buy them from the website.