As mentioned above, you can get surprisingly accurate track estimation by eyeballing it on a hastily-drawn map line (or even a fold in the map in case of a catastrophic pen failure), remembering variation of course.
Measure distances with whatever handy implement you have available (again the pen can work well) against the latitude scale.
Distance gives you time (based on estimated G/S in nm/min adjusted for known or forecast wind - use percentages if you like, eg. a 20 kt headwind would add a little bit less than 20% time to your leg if you cruise at 120 kt, for example).
Time gives you fuel - very important.
Here's the key point though - don't just blindly trust your estimates - sort out a pinpoint a third or halfway down the leg, and adjust heading by the 1 in 60 rule, timing proportionally (eg I was 1 minute later than expected halfway down, so I'll be 2 minutes late at the end ... amazing mental maths skills required).
Consider restricted areas, controlled airspace, diversion radio calls, tiger country you may be diverting over, last light etc.
Liberate yourself from old style nav computers and their digital offspring - nice to have but by no means necessary. Amaze your friends with your mental DR skills.