Since moving from more than 3 decades of greenhouse growing to windowsills and a deck in summer, I have had to relearn a lot of stuff.
One of the biggest pains has been indoor watering - watering the media and not the plants, not spilling it on the floors, etc.
Following suggestions by folks here I put the Gardener's Supply deep boot trays on my rolling benches and I started investigating building a tank-with-pump system for watering. After a while I found that I could buy a 4-gallon powered system just as cheaply.
I ended up getting a PETRA HD4100 sprayer. It has a wheeled cart that is very easy to drag around when full, a variable pressure/flow pump that is rechargeable battery powered (8 hours of use per charge), and it can be separated from the cart, making it a backpack sprayer if desired. It came with several different nozzles, so has broad utility.
I've had it about two weeks now and it has made watering much easier, including a long hose that allows me to water plants high up in a window greenhouse in the kitchen.
It's a bit pricey, but seems to be very well made and checks off all of the requirements.