Just sot shed some lights to all members here so that you all know what the technicians do and what is not..

Coolant change
This I see many time members here say the technician flush the coolant, need 2 bottles to flush coolant...etc

My answer:
Flushing coolant actually does not need to use coolant to flush. What flushing coolant means is that the technician will remove the top radiator hose and feed water from the radiator cap with the engine running. This is to let the thermostat open and the water can flush out the old coolant from the water jackets inside the engine block and cylinder head. This is a complete job. After all the old coolant is flushed out the hose is reconnected and the water inside the radiator is all drain out again. Then only you pour in 1/4 new coolant into your reservoir tank fill up with water, the rest into the radiator and add water. After that you start the car and let the engine run, at this stage you will see bubbles coming out from the radiator cap when the bubbles stop you close the cap. If the coolant inside the radiator is not enough it will draw the coolant from the reservoir tank so correct way to check your coolant is to see the reservoir tank. When the coolant reach the radiator cap pressure coolants will flow back into the reservoir tank.

So after a coolant change, please do check your reservoir tank coolant level the next 2,3 days. If it's within the Min Max level than it's ok. If want to top up just top up from the reservoir tank not from the radiator.

AT/CVT gear oil change or flush.
Some ppl have mistaken the change and flush thing.

For AT or CVT, flushing will need a machine to do the job. The new oil is pour into the machine and the inlet and return hose on the gear oil is detach and attach with the hoses from the machine. The machine will pump in the new oil and push all the old fluid out then with the engine running the technician will go through the gears so that all the old oil will get flushed out by the new oil. To NOTE, flushing gearbox will required more new gear oil then just a drain and re-fill. For drain and-refill you don't flush out all the old oil. The new gear oil will be mixed with the old. Because for AT there's a torque converter which still holds old oil inside the vanes of the TC.

Correct way flushing is done, flush the oils then take out the oil pan and replace the filter so that all the debris during the flushing job is trap inside the filter and then replaced the filter then debris won't get back into the oil passage. Also when flushing is best done if your fluid is not very very dirty, got sand like feel to it and got burnt smell. Please use your hand to feel the oil because if got sand like feel means something is grinding or got part damage inside the gearbox.

Engine oil flush
I believe some know or heard of this before. Shell have this flushing oil for sale at their station now, don't know still have or not since I didn't notice. You pour this in after you drain your old oil (filter don't change 1st) run the engine for 10 mins or 15 mins. Then drain the flushed oil, then change the oil filter and pour in new engine oil.