Simplest method i taught, draw fan lines 5 or 10 degrees either side of track from dep. and dest.. When off track fix position, then add the two fan lines that intersect that point. This is the heading change to reach destination.
Can be reduced to one set or even one fan line once you get use to the method
For timing use quarter or half marks depending on available features or length of legs.
These methods ok for UK terrain.
For crossing deserts or north sea...go buy a sextant, gps or Loran set!
Years ago on my commercial gft i marked on 3min points on my imc leg. when asked where i was these timing marks where spot on with my radio aid fix.
Plan a diversion...drop a straight edge from fix to div., slide to nearest vor rose, throw in a bit for wind, width of thumb 4min little cessna, 3min pa28
Also teach people to guesstimate headings without using protractor.
There are many methods...KIS.