Working signals make a big difference to the look of a modern layout. We build Train-Tech's kit for the 2-aspect version.
In the packet is a sprue of plastic parts that cover all the different signal designs. The leftover parts would make excellent line side clutter. The stick is a ready wired circuit board with a pair of LEDs at the top and power connections at the bottom. A resistor is included to reduce 12v to a level safe for the lights. Not shown, but included is a length of aluminum tube for the post.
All parts are assembled with plastic glues. I recommend holding the joint first with plastic cement, ideally from a dispenser with a long metal tube nozzle like Humbrol Precision Poly. This holds the part roughly in place but with some time to perfect the positioning. Then set it fully with a wash of liquid glue which will thin the cement and make an invisible join (you can just let the cement dry of course, but this tip is for impatient people like me!).
I painted the signal head around the light before fitting to avoid getting paint on the LEDs. Cutting the parts from the sprue took a bit of care and this is mentioned in the instructions, but as long as you use a sharp knife and support the parts, you should be OK. If not, repairs can be made with liquid plastic glue.
Green or Red - painting is simple – Humbrol Matt Black for everything except the post, which uses grey primer from a car spray can. Humbrol No.64 would work just as well, though. Signals don't tend to get very dirty, but dry-brushing the black parts with a dark grey, Humbrol 69 is a good choice, or dusting the model lightly with weathering powders will help it blend in.
The contacts are on a stick 6cm below the base of the signal, which might be a problem if you have a very shallow baseboard. A wiring diagram is included in the instructions so you can connect them to a switch on your control panel.
SK2 Home Aspect self-assembly signal kit - £8.00