I had one and here is how to do it. Everything needs to go with the grain of the stainless, do not work across it. Grain can be restored with Scotch Brite pads as noted by an earlier poster. Clean only with a non abrasive cleanser like Barkeepers friend, Soft Scrub or the like I used to use Bon Ami or Ajax.
Add about a cup of cleanser to a bucket of water. Keeping the cleanser/water stirred while you work brush it onto the car working in in with the grain of the steel. A long handle, tampico wall cleaning brush works well. Do the whole car with the cleanser and rinse VERY WELL with water. Let the car air dry, you are done with the stainless.
Stainless steel looks its best clean with nothing applied to it. Sheila Shine, Newsteel and other similar products are OK for indoor use, outside, they attract dust and the car gets dirty very fast. Outside a Delorean will look its best the longest when it is squeaky clean.
Use regular products on the bumpers, tires, glass and interior. I never found anything that could touch it up. Exterior wash needs to be all in.
At the time I owned the car I ran a food processing plant which had a 18 person cleaning crew whoose main task was cleaning stainless steel equipment. Two of my cleaning crew could do my car in about ten minutes. Its Stainless Steel and needs to be cleaned as such.
