BlueRail Trains has lots of useful articles and videos, plus a fascinating User Showcase web page of several user installs in N, S, HO, On30, O, and hi-rail O, and G scales. Several different approaches have been taken by various modelers, some battery-powered. There's also a user-generated database of locos where a BlueTrains board has been installed.
Better Off Dead Rail is a presentation given by Darby Marriott in August 2019 at the NASG convention, providing a pretty good overview of the state of play in Dead Rail. His views are his own, but much of the information is useful.
The May 2015 issue of Model Railroader magazine had an excellent summary article of the major Dead Rail systems. Included are Del Tang, CVP, Tam Valley, Stanton, and a few others. A good start for a modeller beginning to look into Dead Rail.
Be sure to subscribe to Model Railroader!
Justin Rasas, a Founding Member of the Dead Rail Society in San Diego, wrote an excellent article on our favorite subject for the March-April 2014 issue of Narrow Gauge & Short Line Gazette. A PDF of the article is linked below. Be sure to subscribe to NG&SLG, an great supporter of our hobby. Justin's sage last line was left on the cutting room floor: "Finally, don’t worry about range anxiety; this is not an electric car and you’re not going anywhere ‐ really."
Marshall Stull's Small Model Railroads site has three good articles about dead rail including Dead Rail System Comparison Battery and Wireless Control for HO Scale and Deadrail for Free-Mo. The second article has several useful supplier and info links. The first article shows a complete DCC-Dead Rail diesel installation, with the battery and receiver in a dummy unit, and plenty of photos. The dummy unit includes a battery monitor.
O Scale Magazine's website published an article with detailed information on Dead Rail™, with links to some of the major suppliers.
The March 2015 issue of the UK's Railway Modeller magazine had an informative article about installing and setting up a Del Tang receiver in a yard switcher, plus a transmitter. You can subscribe to Railway Modeller on this page.
The O Scale Resource online magazine -- an information treasure trove on all things O -- has an excellent article on battery power on pages 23 through 29 of the March-April 2015 edition. A PDF file of the article can be downloaded below.
DIY article: How to make a very simple radio control for a battery-powered locomotive out of a common LED light dimmer. No sound, and forward motion only, but the author also provides ideas on how to make a reversing unit.
Dr. Geoff Bunza is a very creative and prolific electrical engineer with extensive experience in model railroading. His article in the November issue of Model Railroad Hobbyist -- unfortunately highly complex and techical -- explains in detail how he created his own radio-controlled, partially-battery-operated locomotive and rolling stock. You can subscribe to Model Railroad Hobbyist here.