Instead of DYI they are making "creative" films for the lomo crowd.
Redscale is done by putting the roll of colour film into the canister with topside and backside reversed. Originally a DYI project Lomo is now selling the reverse film at a premium and Rolli is now manufacturing films with the filter layers reversed also at a premium.
The gel filters are reversed ordered hence the CMY channels are mixed to an approximation
C' = C + Y
M'= M + Y
This example was done by
1) Change RGB positive to colour negative (don't use the grey scale negative.
2) Remix the RGB channels (I don't know it might be better mixing CMY channels
R' = .2R (Y on negative, Blue on positive)
G' = (G + R)/2 (M on negative, Green on positive)
B' = (B + R)/2 (C on negative, Red on positive)
3)Reverse the colour negative back to a positive (here you get a chance to change colour gamma to bring out more yellows and greens)
3)Adjust contrast and brightness curves
If you are using film you could start with a colour negative and skip step 1.
This is my first attempt so it needs some tuning but overall I find real redscale has a creative yawn factor of 8 out of 10 so faux isn't going to be any better.