Get a can of model diesel fuel.
Fill the model tank with glow fuel and suck up to carb as usual.
Prime through the carb with DIESEL FUEL and
with the glow heat applied, hold the prop very tightly and turn it through compression. If you feel a good positive bump you are ready to go. If no bump, you haven't got it wet enough or not enough heat on the plug.
This works well with new engines with poor ring seals and in colder conditions can be essential.