The RAF method for mental dead reckoning:
Max Drift Angle:
MDA=(60/TAS)*Wind Speed
eg If you cruise at 120kts and there's a 20kt wind, the maximum amount of drift you'll experience (ie when flying at 90 deg to the wind) is 10 deg.
Clock face method:
If the wind is 15 deg off the nose or tail your actual drift will be quarter of the MDA (think 15 minutes = quarter of an hour).
30 deg off = 1/2 MDA.
45 deg off = 3/4 MDA.
60 deg off or more = MDA.
Similarly your head or tailwind component. If the wind is 15 degrees off the lateral axis, the head/tail wind component will be 1/4 of the wind speed, and so on.
Glideslopes:
An x degree glideslope is 100x feet per mile. eg 3 degree = 300 ft/nm
For a 3 degree glideslope your rate of descent should be 5 times the groundspeed. eg 90kts 450fpm.
These are just a few little tips. Of course they are approximations but a good enough for real world use and with a bit of practise can be calculated mentally in no time at all. Using a whizzwheel for such calculations suddenly seems ridiculous!