Hi Bill,
I currently use the DCC Concepts flickr free, which I purchase from Bromsgrove Models. To date, I have three coaches lit, (1 x Bachmann Collett & 2 x Hornby Collett). they all use the springs to collect current from the rails.
They are arranged so you have one spring on each axle of a bogie, one axle collecting left, the other right. (DCC Concepts suggest that one bogie collects left, the other bogie right). I then apply to opposing wheels / axle a small amount of electrical conductivity paint which I got from Ebay. (I also use this method to get extra pick-ups on loco tenders!)
However, I am not using decoders in my rakes, preferring them to be on constant. I probably would not recommend a propriety decoder due to the cost of converting a whole rake, let alone all of my stock! - But I have found on the web, an article about making your own, basic lighting decoder. The parts would come from maplins and cost less than £3. Or you can buy it as part of a DIY kit, in which case the chip is already programmed, you just need to solder it all together.
Good luck!