You can ground the source, connect the drain to the desired bias voltage (with a large capacitor - maybe 1uF ceramic) across drain-source) and directly measure the gate capacitance with a battery-powered meter or LCR bridge. The Vishay datasheet says around 0.7nF at 30V and 1nF at 2V Vds (for Ciss).
If you don' t have a C meter, a reasonably small value (maybe 0.5 volt) square wave can be applied to the gate through a suitable resistor (maybe 1K) and you can observe the charge/discharge times to 1/e with a scope (x10 probe), then subtract the scope probe capacitance.