Think about it this way : "What's the difference between a Ha image of the Sun and an Ha image of any other stellar object?"
Not really that much - you may start out with huge quantities of radiation when imaging the Sun, but you will have had to filter 99% of that energy away right at the start, just to prevent permanent damage to your imager in the first place.
So, if by 'preprocessing' you mean 'calibration, alignment and stacking' then you still have exactly the same challenges as normal. OK - if your exposure times are very short (and they may well be), then you might find that there is little, or no, 'dark current' that needs to be identified and eliminated. This would become obvious if you acquired normal Bias frames and normal Dark Frames (that corresponded to your lights) and then examined the resultant MasterBias and MasterDark frames. If they were 'equivalent', then you could simply not bother with Darks at all, abd just use a MasterBias instead. However, you still had to go to all the trouble of cirrectly capturing the Biases and Darks anyway, so why not just use them?
Flat frames are a different issue altogether - the 'source' or 'type' of radiation does not affect Flats, so you are still going to need those to calibrate your Lights. And, when you are performing the 'division' step that is intrinsic to Flat Calibration, you have to have eliminated any inherent Bias or Dark present in both your Flats and your Lights.
So - the answer (in my opinion) is "no" - there are no shortcuts. Not unless, once having acquired all the standard calibration data, you can perform a statistical analysis of your calibrated frames and show that the calibration stage made little, or no, improvement to your final images.
Hope this helps.
