I think that it is very important to eleiminate any gradient before continue as NGC 3628 and M66 have fine nebulosity that could be highlighted.
Do not take the process in the previous example as a recipe as it may be only situable for that image.
As Rick said I would start with DBE placing the samples conveniently to remove the gradiente. I made a try over the stretched .jpg and seems to work. After that CanonBandingReduction. See attached processes.
It is a good idea to use different DBE configuration for each channel and you may obtain a better result in this image.
There aren't any gradients left, but still a lot of background noise.
DBE will not remove the noise, then it is ok to have noise at this step.
I am not sure if I'm doing something wrong here. There is virtually no difference before and after BackgroundNeutralization...
Applying DynamicBackgroundExtration successfully will let you have a quite netural background, then BackgroundNeutralization you will not have to do a big job, that why you do not see so much difference.
Deconvolution. It seems that the generated PSF include only three stars, remember that you must highlight all the stars before exporting the PSF.
You can see how much I increase saturation, but there isn't much color coming out :-(
You can increase Saturation further if you change the "Range" parameter. Set it in a high value and increase Saturation a little more. This will generate a big chrominance noise, but it is easy to remove.