It's nice to keep the current low (so you don't influence the power supply voltage, and so that you don't need huge resistors).
300K across 300V will draw 1mA, which isn't so bad.
For 60V is 1/5 of 300, so a 60K and 240K will do well as bleeder resistors.
The 240K will cook over 1/4 of a Watt while operating, so a 1 Watt resistor will be sufficient.
The 60K will cook very little power, 1/4 Watt is plenty, 1/8 Watt is marginal.
It is commonplace to bypass the bottom resistor with a small cap.