Well Thomas, it's not that difficult to make a "Synthetic Flat" to compensate your images.
I first tried this technique on the BRT Galaxy Camera
some years ago, and it worked rather well.
This is how I did it for my recent comet images taken through COAST's "Clear" filter:
First I searched through the Gallery of recent images and chose thirteen (the more the better) with exposure times of >=2 minutes taken with the Clear filter around the time of the last Full Moon. I carefully selected images which didn't contain any saturated stars or bright extended objects, but where the scattered Moonlight provided a good illumination of the sensor.
Then I normalised this sequence and used a Median addition to stack them. This "averaged out" the stars in the individual images and left just the background illumination, showing up the vignetting and dust-spots:
This Synthetic Flat is quite crude, but works surprisingly well: here's an example of an image before & after flat-field division (contrast-stretched to accentuate the effect):
As for the hot-pixels, I found that I could remove almost all of them using a 3x3 pixel median filter: the stars are spread over a number of adjacent pixels, so they aren't affected.
I used Christian Buil's IRIS
for all this processing.
With best wishes from Ross WilkinsonBolton Astronomical Society