I can confirm that luke warm water works better! I filter the water from the tap, as it pretty hard, so I filter in advance and have a container that is pretty much room temperature the whole time... I have a lot of houseplants, so the water gets used up pretty quickly.
I use one of these things for watering:
www.amazon.de/Bonsai-Gie%C3%9Fbrause-Bal...ds=ballbrause+bonsai
I like how they generally spread the water around. Any thoughts from those more experienced than me?