I use a plastic bucket from one of those dollar stores. It's nice because it has a good handle and a pour lip. It's stirred w/ a long plastic spoon that I bought in a set from the same place. Mixing seems to go quickly, as I use Kodak's recommendations of having my water for the D76 between 120 and 130 degrees F. Just heat the water on the stove in a cook pot, quickly pour it in the plastic bucket, pour the D76 from the package in stages while stirring it w/ the spoon. It seems to dissolve quite quickly. I have the mixing bucket set on the stove while doing this, and turn on the vent fan, along w/ wearing gloves and a bandana over my mouth and nose. Maybe it's overkill, but breathing in that powder that inevitably gets airborne during the emptying of the packet looks like bad news. The fixer is liquid and I simply pour the chemicals and water into a brown plastic jug and slosh it around some w/ the cap on.
Freshly mixed chemicals are stored under the sink in those brown plastic, one gallon jugs from Freestyle (the Dektol goes in the bigger black canisters), or wine bottles. I also use the plastic accordion bottles as I use the chemicals up and have never had any issues. Smaller 16 oz black plastic bottles are used for the developer once the volume goes down, as each bottle gives me the right amount for a developing session, and I can keep the other ones topped up w/ no air space. Here in Florida it gets hot for 6 or 7 months of the year. I was concerned about heat ruining things, but the guy at Freestyle, who originally hailed from here, said just put things in the fridge if it gets over 85 degrees in the house. He seemed to think it was the lesser of the two evils between too much heat and too little. I did it once, but have gone back to keeping it under the sink, and try to use the developer up within a month.
Fill a five gallon bucket with the hottest water you can get from your tap. Submerge the gallon jug in the hot water.
Cold water sinks. Warm water rises. When you put the jug of cold water into the bucket of hot water, it will sink to the bottom. As it comes to the same temperature of the same water it will become neutrally buoyant.
So, just drop the sealed jug into the bucket of hot water and wait until it floats.
Shaking the jug of water every few minutes speeds the process up.
BTW: The hot water temperature at my house is set at 130ºF. (55ºC.) I don't have kids, elderly or anybody else in my house who doesn't know how to check the temperature before jumping in the bath or shower. I can keep the water temperature set where I want it.
If your water heater isn't set high enough to do the job, just use a teapot to boil some water and supplement until you get your water bath hot enough.
I use a Plastic cylinder made for the Automotive trade. It is marked on teh side up to 5 litres and also in US Quarts. the older one Ihave is Branded CLUTHE but the later one has that part of the design blocked out. I believe the Auto folks use them for mixing things like Anti-freeze. Try an Auto parts store. the cylinder is made of heavy LDPE by the looks of it.
I use a magnetic, heated stirrer for most things... One thing not mentioned here so far: A one gallon round, glass "thumb" jug. Simply put the chemistry in and bring the water to the proper level and slowly roll back and forth on a counter top. It keeps the materials in sufficient motion without introducing air from over-stirring and/or cavitating mixers. This was a perfect method in my D-76 days to get a gallon mixed. I would then decant to smaller glass bottles for storing and mixing from.
I use a bit of Xtol and use this method to mix 5 liters into a gallon batch. I've got a pre-calculated grid for my different tanks to get the desired ratio from the more concentrated stock. I've not done any formal testing but I'm getting great life from the Xtol (I don't use much as it isn't my main developer). I've used 15 month-old Xtol stock mixed this way on some film that wasn't important and got normal densities but I'm not so confident that I'd assume good chemistry health and use it that old on important film, though!.