What is better to use to determine the leakage of capacitors?

[tigr]

Moreover, the toy is properly calibrated.

Resistor 0,01Ohm.
A good capacitors.

[Zero999]

For low leakage, fairly large capacitors, there's no need for a nano-amp meter.

Charge the capacitor up to its maximum voltage.

Leave it, with nothing connected to its terminals, for a known period of time.

Measure the voltage, as quickly as possible, preferably with a meter which will take the maximum reading and hold. The input impedance of a 10M meter can be boosted by adding high value resistors in series with it and the actual voltage can be calculated, using the potential divider formula.

Calculate the charge lost and thus the RC time constant and the leakage current.

[tigr]

Yes, this is an acceptable method. But only if we can not measure leakage by other testers. It is necessary to take into account the fact that leakage is more difficult to determine than ESR.
The old proven method, which is still used by  repairers, is an analog tester. The only limitation is the test voltage of 3v.

[tigr]

As we can see, all ESR meters respond differently to a capacitor with a very strong leakage.