Sharpening is a habit, not a project
Five minutes at the stone every time the tool goes back on the shelf beats an afternoon of grinding once a year. The hard part is the habit.
Buying at markets without regret
Cracked castings are worth nothing and look identical to sound ones under rust. I carry a small torch and I tap everything, which makes me look eccentric and saves money.
Flattening a sole without a surface plate
Float glass and wet-dry paper. It is not a machinist's answer but it has never let me down on a wooden bench.