When I tried to flush the downstream lines from my PSD pump, I took apart the slave cylinder to check its condition. This is what I found.
Are the blue seals in the slave cylinder supposed to be continuous rings (like "O" rings) or are they designed with breaks in them (like cylinder rings)? They're like having a 30 degree angle cut.

The central seal is the actual seal and the back up "rings" are just used as guides to prevent the metal piston hitting the wall of the cylinder and scratching it.

Here's what we're starting with. A new seal kit and a disassembled slave cylinder

This piston has the new seals already installed. The two "seals" on either end of the piston are wear rings and don't require an explanation to install. They are split and their orientation does not matter. Simply remove the existing two from your piston, discard them and replace with the new split rings from the kit. Their purpose, as I understand it, is to keep the piston straight in the bore, prevent rocking and take the brunt of the wear. Their function is not to seal. The center rings (an "O" ring and a Teflon seal ring) are what I am installing. I used the following professional tools:

The first is a Craftsman 3/8" long socket. I found the outside diameter of this socket to be perfect for what I wanted it for. The smaller end was the same size as the seal ring ID and the larger end was the same size as the piston OD. The taper was smooth and the price was right.

Next, I needed something to drive the ring up the sockets shaft. I used a piece of 1/2" electrical conduit because that's what I had and it was close enough in size. I had to bevel the driving edge because otherwise it would stop just short of pushing the seal over the expansion part of the socket.
Here's what that looked like:

Next, I needed something to align the wide part of the socket and the piston, so I could push the expanded ring from one to the other. I used a piece of 3/8" rod. Again, it was pretty close to what I needed and kept the alignment I needed.
 


When placing the seal onto the socket make sure the ring is oriented as shown. The smaller step in the same direction as the smaller part of the socket

Next, I placed the conduit over the small end of the socket and pushed the seal down to the part of the socket that widens.

Now I stood the whole assembly up on the table and applied heat with a heat gun. Be very careful, as a little heat is all that is required to allow the seal to stretch onto the larger end of the socket. A hair blower would've been a better choice, turning the socket to distribute the heat evenly. Once warm, I used the conduit to push the seal onto the larger part of the socket. The seal stopped right on the edge of the larger part of the socket. I couldn't photograph the pushing because I needed one hand to hold the heat gun and the other to push the conduit. I wore gloves because the socket got hot.

Here is the seal on the larger part of the socket, then with my hands I pushed the seal to the bottom of the socket
 


Next, we knead the seal by hand from the socket onto the piston. I found that to having the wear ring installed in the notch that you have to pass to get to the center notch eliminated any problems with the seal ring getting caught up in that notch. In the first picture below, the previously installed seal ring is still in place. I cut it out at this point, as you can see in the next picture. Don't forget to roll the "O" ring into the center groove (from the opposite side of the piston) before rolling the seal ring onto the top of it. This part of the installation is complete. The heat expanded seal ring felt loose and a little sloppy in it's groove at this point.
 
Next the slave cylinder goes into the vise, where we drop in the spring, followed by the piston, up to the point at which the seal ring, which is expanded, stops it.
Now I took a small jewelers screwdriver and started compressing the seal ring into the bore, turning the piston as I worked the ring. I tried not to push down too hard on the piston, as it made it harder to compress the seal ring. It went in after working it around the edges for about 15 seconds. It was stiff in the bore, but able to be moved. With the piston in, it should look like the last picture. Again, with one hand turning the piston, and the other compressing the seal. I wasn't able to take a picture.
 

 
Now it's just assembly. Replace the washer and the C clip and you're ready to re-install the slave cylinder.
I'm sure these methods can be improved upon, and if anyone has anything to add, correct or suggest , all input is appreciated.
To those who purchased these seal kits from me to install in the future, if you have any problem installing them, contact me.
 
MrLexse