Good advice here.
You will never be test ready if you have 3 month layoffs each time.
Planning - make life easier the night before / in the morning. Pull the F215 and synoptics before you leave home (just make sure they're valid for the flight). You can also do runway performance.
Diversions - if you can't make a sensible whole number cruise speed (60kts or 120kts corresponding to 1 or 2 miles/min) have a cheat sheet made up with the time and distances worked out (IE 5nm, 3min at 100kts, 10nm 6min at 100kts). Doesn't matter if you like being precise - if you can't do it, don't make work for yourself.
Lastly, fly the aeroplane. Sounds simple, but oft forgotten.