I just wanted to give a review of Caswell's Stainless Steel Blackener Kit.  For a long time, I'd wanted to swap out all the SS small parts on my CDP for blued/black  ones, but it was going to be costly (around a $100 or more).  I did some research here on the forum and found some people that mentioned Caswells SS blackening kit and it was only $32 w/shipping.  So I figured it'd be worth a shot.  Here is their info, 
www.caswellplating.com - p/n ssbgk
IMO, the kit works great.  Some parts I had to repeat the process a few times to get the look just right.  The finish is exactly what I was looking for.  I cannot say how durable it is yet, but to me, it looks great and gives me the look I was going for.  
Once I figure out how to protect the frame from the chemicals, I will do the plunger tube for a complete look.  Oh yeah, I have to get new pins also.
I apologize for the crappy pictures as I am not good at it.
Before
 
After
