Copying color negatives with camera

Ok, looks like your on the right track, yes those CC filters are silly expensive, but a cyan gel should be fine over the flash, I use the CC filters over the flash not the lens, though high quality kodak CC filters really don't seem to effect sharpness at all, they are very very thin, I use them because I can get very precise correction, down to 5CC units.

As a starting point, and It is not precise as each camera is different try setting the WB to around 3800 k, leave the magenta/green tint on zero.

Shoot by manually setting the exposure, then open the RAW file invert it, drag in the black and white points to give the proper contrast range and then have a look at the colour cast.  If the cast is cyan, (which is basically what I think your test file is) add more cyan too the filter pack and slightly increase the exposure to compensate.

If its red, add more red etc, remember its a negative process so we add the same colour as the cast.

Ideally you should be able to get to a point where the inverted file is very close to correct without any further colour adjustment of the midtones, the highlights and shadows may need a very slight tweak, but if they need large adjustments you are probably over or underexposing one of the channels.

It is trial and error but the end result will be a setup that gives minimum file noise and maximum colour information with the most post edit options, it will be worth the effort and you have made a great start.

all the best

Brad