We also have a package that includes both of those plus spare o-rings and lubricant to maintain them here
For any carbonated drink especially (beer, cider, kombucha, soda, G&T, rum and coke etc) it's best to chill the inside of your keg before filling. This will prevent foaming and loss of carbonation when the liquid hits warm metal.
With an insulated keg it's always best to chill inside the keg before filling as otherwise you may warm your drink a bit and once it's in the keg it takes a long time in the fridge before the inside starts getting colder.
It's best to flush the inside of the keg with CO2 or nitrogen before filling it to avoid your drink touching oxygen (it's only really important for beer, but it's best practise for all drinks).
You can do this by injecting CO2 into the open mouth of the keg or though the gas post and pulling the gas release valve a few times. CO2 is heavier than air so imagine your keg is now filled with liquid, the heavier liquid (your drink) goes to the bottom and lifts the lighter liquid (CO2) on top of it as you fill. This prevents your drink touching oxygen while you fill.
You can absolutely fill your keg from cans or bottles, it's not the main reason we designed the mini keg (we'd like to prevent as many cans and bottles being used in the first place as possible) and it's not the best method but there are good reasons why you might want to:
Pour from a beer tap. Most people prefer a pub quality draft beer over a can or bottle, plus it looks cool!
No chance of broken glass in the pool, on the beach, in the park etc.
Stays cold all day without needing to cart around an esky and ice (when using an iKegger insulated keg)
You can transfer straight to a keg while at the shops and get the money for the cans / bottles back straight away. No rubbish piling up at home.
Don't need to bring alll the rubbish with you (great in limited space like a caravan).
Don't need to bring the rubbish home with you (if you are going into a national park, camping, on a boat etc)
Chill the keg, with lid off for an insulated keg.
Flush the keg with CO2
Tilt the keg and pour slowly and with as little splashing as possible down the inside wall of the keg.
Screw the lid on, attach your regulator to the gas post and put more CO2 in while pulling the release valve a couple of times to get rid of any air that did get in.
Pressurise to the correct pressure for your drink (about 12-14psi for beer, 15-17psi for soda / mixed spirits).
You can now disconnect your regulator till ready to drink.
This method has the most chance of oxygen contact and you should be aware that craft beer may start to go bad within 48hours if you aren't careful (bulk breweries like Tooheys, XXXX, Carlton etc heat treat their beer and it will last longer).
For canned and bottled sodas and RTDs (and making your own mixes) like G&T, Scotch & Dry, Rum & Coke etc a bit of oxygen contact will have no affect, just maintain the pressure in the keg and they will stay fresh and carbonated.
Filling From A Beer Tap
Sanitise your keg
Chill the inside of your keg (if at a brewery ask them to put it in their fridge for a while before filling.
Flush your keg with CO2 (many breweries will do this themselves but ask them beforehand and do it yourself with your regulator if they don't. Unless you plan on drinking the keg within the next 24-48 hours).
Attach a hose to the tap that reaches the bottom of the keg so you are filling within the "cushion" of CO2 and with minimal splashing.
Once filled (it will probably overflow with foam for a bit before it's liquid to the top) screw in your cap or even better screw in a spear and again flush the filled keg and pressurise to 13psi approx.
You can now keep the keg in the fridge till you want to drink it, the more careful you were to have no oxygen contact the longer the beer will last. At worst 24 hours for an unsanitised, unflushed keg up to weeks for a properly sanisited and carefully filled flushed keg.
Sanitise, chill and flush your keg with CO2.
You will need to leave your spear on the flushed keg and pressurise the keg to approximately 12psi.
Ideally flush the filling line with CO2 as well.
Disconnect your regulator and attach a flow stopper / spunding valve or iKegger BeerKeeper valve to the gas post.
Attach the liquid post of the keg to the filling tap via a beer line.
Turn on the filling tap and adjust the valve on the gas post till it is allowing a slow steady flow of gas to escape as the liquid fills the keg.
If using a flow stopper or ikegger BeerKeeper the flow will stop automatically once the keg is full so simply turn of the tap and disconnect everything once done.
If using a spunding valve turn off the tap once liquid starts coming through the valve.