I bought an old Star 30M a few years ago, it looked OK in the pics on the auction, but when I got it, it had been "lubed" with WD40, and had the trigger almost totally frozen due to the gunk the WD40 formed. I took the gun apart, and put some Dawn dishwashing soap in a pot of water and simmered most of the internal parts for a few minutes, except the springs, which I took to a friend's jewelry store and had him put them into the ultrasonic cleaner. After all the parts were done, I tried to use brake cleaner and some other stuff to get the crud out of the frame, but the slide and frame went into the ultrasonic cleaner too.
Once everything was cleaned, I soaked it all in Mobil 1 oil for a little while, and put it together and shot a hundred rounds through it. I sure wish I didn't have to sell it a couple years ago, it was a great gun, and once the WD40 crud came off, it looked almost brand new.