Here is how to do this. Depending upon how old the film is, you rate it accordingly, giving more exposure as needed. Older film, as well, will require more development time and/or more developer strength.
Basically, you need to develop the film more robustly because of the diminution of silver, but you can still acquire a good negative. There are more steps involved, in that, after fixation you need to 'blix' the film in order to 'bring back' that nice orange mask back into transparency.
I find Dektol superb for doing this; you will have to process films a few times before you nail down your procedure, I suggest you expose a roll, then cut it into segments of a couple of inches (in the dark, or course) so that you will have multiple tries for one roll total (Why waste so much film?) You can start with Dektol diulted about 1 + 19 and work from there, choosing a convenient (ambient?) temp and time (how is 8 minutes?). After the development, stop, and fix, then blix, you will be in a position to determine whether you should modify your Dektol dilution and/or development timing, and film exposure, (but not before after you are finished blixing). You are looking for a good negative that will print well, so, as with B&W, you want shadow detail and good differentiation between highlights and shadows. NOTA BENE: with that orange mask you might have to opt for a bit more contrast in the neg, as that mask can serve to slightly filter your VC paper into a lower grade.
Again, when you process C-41 film as B&W, (yes, even E-6 can be done this basic way) you acquire an extremely dense negative that most will simply discard (because it is so ugly). Holding it up to a light bulb, however, will reveal a real image. Let's say that the film involved is not too old and is rated at ISO 200. So you expose at that speed in your camera, then process as usual in a robust developer, normal stop bath, and normal fixer. You are rewarded with a dense, ugly mess that depresses you greatly. Now comes the magic: the blix.
Make a bleach solution (which keeps forever in a bottle, if not always kept in bright sunlight). I use volume measurements but for this, potassium ferricyanide, one gram does equal one mL so it does not matter. Mix five mL of potassium ferricyande into 500mL of water (i.e., 1 mL per 100mL of water). That is your bleach and, kept separate, keeps forever. To make blix, you will add bleach solution to 'paper strength' fixer at one part to one part, but only just before using it, as the combination will not keep for more than maybe 30 minutes. This blix serves to remove all that fog density in order to reveal the image as you wish for printing. You keep that film in the blix (agitate normally) until you see a brilliant orange mask emerge (anywhere from a few minutes to ten minutes, so be careful). This is important: you want to watch everything visually, so you might be advised to cut a roll length of after-processed film into many smaller segments and do this blixing in a shallow dish, making certain to agitate in a uniform fashion (in full room light) as you don't want one part of the film to blix faster than another part. Excess blixing will remove ALL density. (You STOP the blixing procedure by dunking the film back into the fixer, or simply use a water bath.) With experience you might dilute this blix further in order to create a suitable blix time.
Much frustration and much effort will be needed with trials in order to achieve what you want on a consistent basis. Many out there do not like my efforts because they require thinking outside of the box and don't heed to the tried and true ideologies. But, done properly, you will achieve 'Golgonda' with beautiful negatives which capture clouds without needing other filtration. Older films, years older perhaps, require both more exposure and more robust development. For these, use stronger Dektol, maybe 1 + 9 or so. You might even need longer fix times, but remember, when fixation is complete, but before blix, the negative WILL BE DENSE. You can best judge completed fixation by looking at that negative with a light bulb behind it and a magnifying glass next to your eyeball. Good luck. - David Lyga