Microlighters

Hi guys.
But of a novice question, please dont scold me....

So, i am curious, what would be the simplest way to check my trike's fuel burn? I dont exactly want to plonk in 30l, fly a hour, drain the tank and see whats left. Is there a easier way, or is that it?
Thank you in advance!

Fill it up.
Go fly.
Record flight time.
Fill it up again.
Make the calculation.

If we are talking about a trike, I know of two additional options, or you could do a hybrid of both.
1. You drain your tank and fill it up in suitable increments, lets say 5, 10, 15, 20 liters, mark the levels on the outside of your tank. Go fly and see where the level is after flying.
2. Drain your tank, weigh your plane with bathroom scales, fill 10 liters of fuel, weigh it again, calculate the weight of fuel( I suppose you could google it too), fill it, go fly and weigh your trike, calculate the missing fuel.