Have you read the info [MENTION=78273]Jeremy556[/MENTION] posted? What you're suggesting does not provide a way to add fluid or bleed the entire line from front to back.
You have to bleed the system from the center outward. It takes a pump with a large reservoir that can keep pumping fluid until it reaches the pistons at both ends. The tanks at the center have intake connectors for the SST and bleed valves for doing this. The pistons must have a bleed valve at each end. There's no way to input fluid at one end and keep pumping, afaict.
I'll admit I haven't read the entire instructions or gone to all of the detailed links with in-depth instructions for every step, but I scanned the whole link and got the jest of it.
If you blindly follow the Toyota service manual - then I suppose there is no other option. In my experience SSTs are handy and expensive. If you're a pro - you should have them. For the rest of us, I've found most SST tasks are easy to either replicate or work around. Timing belts, rear wheel bearings, axle seals, etc can all be done pretty easily without a SST with a little ingenuity.
Unless Pascal's law has changed, the KDSS system - or any hydraulic system - can be pressurized from anywhere in the system. There's no reason you *need* to either combine the bleeding with the pressurizing or bleed from a specific spot. I think it likely is the best method to bleed from the central ports, but that does not in any way prevent pressurizing the system separately.
Pressurizing is basically pre-loading a nitrogen spring. So long as you bleed the system to the proper volume of fluid, it should be possible to pressurize it with the piston that's already on the vehicle. It may not be quite as easy, but it should be a possible option. I suspect some trial and error would be necessary to test and find out exactly how much fluid (ie, when bled, where the pistons sit with no pressure) before someone could do a writeup on how to reliably use this method.
The advantage is that all you should need would be a hose with the proper fittings and a reservoir for bleeding. I would build this out of something like 3 or 4" PVC pipe with an air fitting so I could put the fluid in, and pressurize it to low pressure to bleed the system just like I would brakes or any other hydraulic system. Once it is bled properly, I would then need another hose with a pressure valve that reads up to 450psi, and a very small port valve to release pressure. Then open the shutter valves and start jacking up under the piston. Once you reach 400psi, you start releasing fluid pressure very slowly to let the piston reach its appropriate position and maintaining 400psi line pressure. Close the shutter valves. And you should be pretty darn close.
One possibility is that the two pistons do not have enough volume of fluid in the stroke to reach the necessary pressure. I don't know the answer to this. I think we can calculate it, but I don't know the stroke or bore of the KDSS cylinders nor do I know the volume of the nitrogen chamber.
Alternatively any hydrostatic test pump with the correct fitting should do the trick as well for a lot less than the SST. I think for the 4runner KDSS you don't need the manifold and dual hose system, but I'm not entirely sure not having done it. I *think* the 4runner version only has ONE fill port, not two like the Land Cruiser version. In reality this is what I would actually do. It's $100 for the tool. Should be pretty easy to do. Much easier after thinking it through than using the existing cylinders. And by the time you buy a pressure sensor and hoses, etc. you're not far off from the $100 pump and a fitting.
If I were Marshal and had insurance paying for it - I wouldn't even consider trying it myself. This is just to hopefully put to bed the idea that KDSS is some magic system that can only be filled with unicorn tears.
