There should be a sticky at the top of the page, as this question is asked often... and for very good reason. First off if your not having any problems now.. I sure wouldn't tempt that by installing T's into rubber hoses, in my opinion this is just asking for problems, sure they are probably just fine, but when you start messing with hoses that may be a little old already, and that was just for fun the main point is I doubt you need any flushing unless you have noticed problems, if so then by that time it prob needs some attention... but here is the way I do it for a simple, no harm done, easy, cheap coolant change.
Pick your coolant, this is no easy task in itself !1 with all the coolants you have to choose from now, and what your manufacture recommends, do some research on this... if in doubt you can always purchase the coolant from your dealership which I do this for my Honda... it's a bit pricey, but it last a long time, and I don't have to worry about having the correct coolant make/build... by the way it's the Honda blue, I'm thinking I get a few extra horses just from that probably like 15 hp or something (this extra hp part is just for fun LOL)
Go to walmart get some distilled water, you should have already done your homework to check your cooling system capacity, get enough to do an entire coolant change, and then 3 more gallons, it's very cheap around 50 cent a gallon.. Remember distilled water, not drinking, or any other kind, and don't use tap water, you are taking a gamble if so by introducing a lot of chemicals, getting your cooling system PH off balance etc etc, and I have done this myself ending up with a huge mess in a very short time.
I would then dump the rad drain (please catch the used coolant as it kills dogs graveyard dead in a slow, very inhumane way.. bleeding the guts out) cats or whatever else, and they love the sweet smell. Fill with distilled water, drive around for a day or so if no cold weather, then drain again, repeat drive around, do this until you get clear water from the drain, and you can be sure that you have cycled everything good by driving to get up to full operating temp, and at least 15 minutes after that ( but the 3 day drive is much easier of not hard pressed to do this as you can do a 5 minute drain/fill with distilled water the your normal driving routine for 3 days) Also remember you need to cycle your heat during this time, run it at max heat, max fan etc for as long as you an stand it, and at least 10 minutes at full operating temp to clean out your heating system, and getting fresh coolant in there as well.
After getting clear water draining out, sit down with a piece of paper, and calculate up your cooling system capacity/ and how much you will need to add to bring it up to what you desire. 50/50 or stronger ( I go stronger 70/30 but I doubt it does any good unless you live in sub zero or worse temps LOL.. however it may offer more corrosion protection for the cooling/heating system..) If all you can get is 50/50 then it's no big deal just add enough to equal what the manufacture says your cooling system capacity is, then I do another half gallon flush/fill over that at least ( just depends on how much drains out, and where I'm at in bringing the system up to par) that way I know I have very close to the 50/50 mix which is the best you can do getting premix. Now on the good stuff straight coolant it's even easier as you already have you cooling system filled with distilled water, just drain out enough water ( drain in a catch pan, pour in a gallon jug that you should have plenty of now after all the walmart distilled water empties). I like to write down on a piece of paper how coolant I will need to add to my system using this method, and then make a small check list as you will likely have to drain more than once ( three times seems to be the trick here)
Just doing a simple cooling refresh, this is very easy thing here.. drain the rad, if your purchased premix 50/50 fill back up, if the good stuff straight coolant I would measure it out, and premix it with distilled water to whatever your choice is here 50/50 or 70/30.. it's very simple to do this way in my opinion premixing your straight coolant with distilled water you just need a clean gallon jug.. use your distilled water jug, pour your distilled water in a kitchen container/pitcher etc.. I would do at least two drain/fills this method to get enough fresh coolant in the system unless you are already doing it yearly/ every other year..
I got long winded, but I plan to copy this, and save it as many people ask for tips etc, and this is the best method I have found, and it is very easy, fast, and no mess. The walmart distilled water is the key here, very cheap... now you just need to pick your coolant... Don't forget your heater (use it wide open heat, and temp) and also clean your overflow bottle out if you can, and clean under side of your rad cap, replace if needed.
Hope this helps
