Toy train operating and collecting

The manual says I need an external power source for accessories. And I'm only running accessories so I programmed out the switches. Okay so far. But the manual also says that if I'm running accessories only I can use the power pack for powering the accessories. THIS DOESN'T WORK. Unless I run a power wire to another transformer and a ground wire between the SC-2 and the transformer (i.e. the typical wiring diagram shown in the manual) my accessories are dead. What gives? All the extra wires I'll need for 4 accessories are making me think the SC-2 is a waste of time. I can just hook up those cheap little red switches that come with accessories and be done with it. This probably explains why the guy who sold me the SC-2 never used it.

 The SC-2 is a "box" with a set of remote control relays.  You need power to run the box (aka the radio receiver internal to the unit) and then you need power to drive the relays.  This is what they mean by external power like the wall wart power supply or use of the AUX  terminal on the SC-2 itself.   Most accessories are powered (they wouldn't do much if they weren't) and they still their own external power supply.   All the SC-2 does is replace the on/off or activate/deactivate button that normally comes with the accessory. 

The problem is that accessories come in two main flavors.  Devices that you just turn on and they run their course (aka momentary contact) and devices that need to be "held down" (aka continuous contact.   If the device you are trying to control isn't in the back of the SC-2 manual (there are 14 examples) or the back of the ASC controller manual (another 6 or 7) and it isn't a Lionel accessory that has instruction on how to wire it to an SC-2 or ASC you will have to figure out what type of connection(s) are being used and the "pin outs" from that accessories controller's activation switche(s).  It took me about 1/2 hour to figure out how to wire up the MTH automatic passenger startion.

Thanks for the quick reply. Just to clarify: if the accessory I'm trying to wire is shown in the manual (my first one is the Lionel water tower) I have to wire it exactly as shown? Sounds pretty dumb as I write this, but my thinking process is as follows:

I've read on this website that you can create jumpers for the common terminals on the SC-2. I understand the terminals are not connected to each other internally. Do the jumpers allow for just one common wire running from the SC-2 to an external power source? Otherwise, I don't see the point of the jumpers.

BTW, my wife bought me the MTH freight station for Christmas. Very nice. I don't know if you have any experience with it but one switch activates the lights and I presume the other switch would be considered momentary since you hold it down to activate the conveyor belts.

 The relay contacts/terminals on the top side of the SC-2 replicate the switch contacts of the control mechanism for the device(s) you are trying to activate/control.  You can actually wire up accessories switches/buttons in parallel to the SC-2 so someone standing near the device can run it.  You can even run a second controller back to a console and then trigger/control the device from the CAB-1/CAB-2, the control panel and the site where the device lives. 

I don't mind spending a little extra on wire especially if it avoids confusion/complications.