as a pro window cleaner i recon the way to go is using a mop and squeegee.
use sunlight dishwashing liquid in a bucket, about the same amount as you would to do the dishes maby a little more.
a window mop can be replaced by a clean rag, small towel, or even the dish cloth.
what ever you use, ring it out so it stops dripping, then rub the glass all over untill you get a soapy bubbly lather over the front of the tank. now get the squeegee and in one steady fluid action pull it from one side to the other. never stop or start in the middle. wipe the blade with a clean dry rag and repeat until done (two maby three strokes).
if you keep getting streaks wipe the starting edge of your tank as well as your squeegee between strokes.
dont hesitate as the soap will quickly dry and needs to be sqeegeed asap.
now wipe only around edges and your done, hopefully.
you can buy a squeegee from the department store, supermarket, warehouse or even a cleaning supply shop.
if you are concerned about bubbles getting into tank, you can leave the top one or two cm soap free.