The simplest, least expensive, and fool-proof DIY glow driver is to simply insert a standard servo in the positive wire between a 1.2V battery and the glow plug. One end of the positive wire is soldered to a inverted "U"-shaped piece of brass epoxied across the top of the servo case. The second end of the positive wire is soldered to an "L"-shaped piece of brass screwed to the top of the servo arm. The short leg on this piece of brass should be bent to curl under the servo arm such that when the servo is actuated, the brass on the servo arm contacts the brass on the servo case. Several of us have used this for many years and contrary to what one might think, there is no interference (even on 72 MHz) when the 2 pieces of brass contact or separate. Simply set up the servo on one of your transmitter switches and you can also mix the channel with throttle if you also want it to come on and off with low throttle.