I've never had a problem and I use a 10 litre bucket. I fill it to the brim but pour the water back in slowly. Eventually you'll work up some forearm muscles and it'll be a piece of cake
I refill with the bucket method and have never disturbed my sand or plants. I float a large plastic bowl on the water and fill the bowl with the incoming water. One hand on the bowl to keep it from sinking more than just below the water line. The water overflows from all sides of the bowl and doesn't cause any disturbance with the sand, fish, plants, etc.