Hi 767 Bill
Basically what I have been doing is the double and half rule that I was taught or to use the 1 in 60.
That was to use those 10 degree fan lines on my chart.
If I was ever off track which has happened
I would see if I am either 5 or 10 degress lets say within those fan lines.
Double that figure and then half it when I get back onto track.
So if I had a track of 300 and was off track by 5 degrees port, double this to 10 degrees and add to make it 310. Followed by half to 305 when I get back on track at the next way point.