The advice you are getting about solvents for cleaning are directed toward pre paint cleaning, not in between coats.
DO NOT use a solvent such as lacquer thinner, mek, brake cleaner or other except to clean oily residue off the part before you start, and let it dry well before priming.
After your primer dries good you are going to be looking at wet sanding between coats to level the finish. That's where the prep spray you are talking about comes in. For my stuff I just blow the part off good with compressed air from an oilless compressor. If you don't have one then you'll need either some electronic parts blaster (air in a can) or an in between coats wash of some kind. But the solvents mentioned above will lift or melt your finish, so that's a NO NO. If you are diligent you can clean it up with a tack cloth. If you feel more comfortable with a wash cleaning I'd find an automotive paint store.
What ever you use for in between coats, wear a pair of clean gloves as mentioned to avoid leaving oil off your hands.
Good luck