My Process For Small Plates

Here is my process for etching small brass plates. I haven't been as successful with this process for larger (2"x7") plates. I'm dialing it in for those large ones and will make a new post when I have it.
Please read about the safely handling the PCB Echant!!!!!!! I'll provide some links at the end for this information. Use goggles and be careful.

Metal Surface Prep

1. I cut a piece of metal about 1/2" larger than the intended etch. It wastes some metal but it more than makes up for the waste in the time savings. I use these to cut the brass.
2. I use 220 git sand paper to remove the top layer of the brass. I make two passes that are perpendicular to each other.
3. Wash the plate with soap and water.
4. Dry plate with clean towel or paper towel.
5. Clean surface with acetone. Two passes usually removes anything left.
6. Let it air dry. 

Image Creation

1. I use Inkscape because it's open source. Twyst prefers Illustrator. Image must be black and white no grays or colors.
2. You can use pnp blue or just printer ink. The pnp blue costs more but the level of detail is high. The straight print ink gives a very aged rough look. It doesn't provide as good a resist as the pnp blue.
3. Laser Printer. The laser printer ink is a must or a copy machine toner I've heard works too. I bought a used Brother's laser printer off craigslist for $30.
4. Print image.
5. Cut  to size and tape pnp blue over image. Shiny side down. My printer doesn't hit the previous spot exactly so I always leave about 1/2" of extra pnp around the image.
6. Load paper back in and reprint the image. I use the highest density print - 1200.
7. Print.

Laying Down Resist Mask

1.  I use some painter blue tape and tape the pnp printed down to the surface of the metal. Shiny side up. This is where the extra surface area comes in handy to grip the tape.
2. I then run the plate through a laminating machine. I bought this one from Amazon. No tax and free shipping with prime. I run it through 5 times.
3. I then rub the top of the pnp blue with a hot iron and apply pressure. You'll have to figure out what works best for your iron mine is set at 4.5. Not too hot. I think I've read like 235 degrees. I use the front of the iron to rub down the resist. I can tell when it's good when the cloudy black image turns a deep black. This takes 3 min or so to rub it on.
4. Water bath. Let it cool for 3-5 min.
5. Peel it up. 
6. It took me a number of tries to learn the correct temp/pressure/method. You will just have to experiment and learn what works best for you.
7. If you are just using the direct ink method I just use the iron on the same setting and iron the paper onto the metal. Then after the water bath you have to remove the paper as it is stuck to the ink and plate. Use gentle pressure and rub it off with you finger tips. I also use a soft brush toothbrush.
8. If you don't get all the mask applied you can fill it in with a sharpie. I then cover the sides and back of the plate with sharpie. 

Taking the Plunge 

1. I then heat up some water and place the bottle of etchant into the hot water. I've read like 130 degrees. 
2. I suspend the plate upside down with tape in a plastic container. Then pour the etchant in just enough to cover the plate.
3. Shake the container to remove air bubbles. Then shake it every few minutes until you're happy with the depth. I usually give 30-60 for an etch.
4. I then wash the plate off saving the water for proper disposal. 

Finishing

1. I then use a green scrubby and take off the resist from the plate. I do it in the sink as I've already washed any echant off before.
2. Then I wash the plate with soap and water.
3. I will use straight vinegar, salt and vinegar, or salt water as patinas. I use a small paint brush and rub on the solution letting it dry in the sun. Repeat until happy with the color. You can also place the plate on the stove to really speed up the process. Experiment.
4. Then I'll sand off the top layers of the patina to expose the brass. I use 400 or 600 grit sandpaper. Also sometimes a fine steel wool to polish it up shiny like.
5. After I'm happy with the color I'll apply wax. I use carnauba wax but others use other waxes. I haven't experimented with other waxes yet.

Links:
http://steampunkworkshop.com/electroetch.shtml
http://etsymetal.blogspot.com/2009/06/etching-brass-and-copper.html
http://www.instructables.com/id/Etching-brass-plates/

Youtube
http://www.youtube.com/watch?v=8fBlYEKqsRo
http://www.youtube.com/watch?v=GSxRE0k2D4w&feature=related