A lot of people here use the "Python Np-Spill Cleaning system", it is fairly pricy, and is basically a large roll of tubing that connects to your faucet or where ever, and automatically siphons out water from your tank, and send out water from your faucet/tap, so it makes for quick and easy water change. In short, it works and improves on the siphoning principle, it's automatic.
But for others (like me) I do manual siphoning of water, with lugging buckets of water around, it's pretty tedious, and time consuming, but its the good old way used for years,

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Not sure about the garden hose thing, but it is probably related somewhat to siphoning the water.
Most turtle water doesn't need a secondary cleaning agent, just clean water and a cloth, but in the event that there's something nasty that conventional methods can't take care of, using basic vinegar is a safe disinfectant (but you should still rinse and clean it out thoroughly, too much is bad for your turtle). Some users do complain of the smell afterwards though, your choice. Another option is to use very dilute bleach to clean your tank, about 1 part bleach to 10 parts water, but be very sure to clean it out, as bleach is also toxic to turtles (as with us). Soap is not preferred, because it can stay in your tank without you being able to see it.
The average user does a partial water change (anywhere up to 25% or 50% of your tank water, though I only do about a 15% water change) once a week, though some people change every few days if time persists. This depends on how messy your turtle is though, sometimes partial water changes can be done less frequently, and sometimes more (if you have multiple turtles, or they are just plain messy). A full cleaning is on average one month, and with partial water changes, can be less or more. Filter mantenance is also the same, less or more depending on the turtle (some people check their filter for performance every few days/weeks and take it from there).
Hey hey hey.