I haven't parted out any Porsches, but I have had very good luck finding some one off parts for my 964 over the years on E-Bay. In posting questions about a set of parts recently I struck up an offline conversation with one seller who appears to be making a business of it. Here is a link to his E-Bay store for just the Porsche parts listings (carries other makes):
S Auto Parts items - Get great deals on 88 Porsche 911 windshield washer tank cap items on eBay Stores!
I think he is somewhere in the Northwest and he says that it takes him about 4 full days to part a car in decent condition. From a complete car he says he can get about 300 "parts" to sell on E-Bay (some are obviously groups of parts, i.e. intakes, exhaust, etc.). What I find sets his store apart is that most of the parts are auctioned with real-world starting bids, the parts are clean with good photos and descriptions, and items are well packed and shipped very quickly.
I've often considered parting a car out for some extra cash, but once I do the math it doesn't seem like it would be worth all the time and effort. You would need quite a bit of space to keep all the parts organized and you would have to be pretty sharp on shipping costs (especially with odd shaped and heavy items) to maintain your profit margin. I've always thought that you might be able to make it if you worked it with more than one person with each person "specializing" in either parting, managing the E-Bay or CL postings, shipping, etc.
No disrespect to our gracious host intended in this response.