put a large kitchen mixing bowl in the tank to put water into from what ever source you have,.. it will help displace the force of water and flow out softer than from a hose,.
i just bought a gravel vac thing today, was 80 bucks but hooks to your sink and fills from it and cleans with it, it is AMAZING!!!!!!!! i did a 25% water change [without gravel cleaning] in 5 minutes! it was AWESOME!!!!! IMO get one!
I use the ladder from the walk-in closet and set the bucket on top. Then I just combine the awesome power of a gravity with a the gravel vac to fill it in. I place the tube going into the water either over driftwood, decoration, etc so it won't mess up the gravel/sand.