The filters are cheap for the aeropress. I don't use mine often because it's 1 cup, no sh!t, but it does make the best coffee. I bought 2 packs of filters and it will probably last me longer than the press.
The upside down thing is just like it sounds. You put the plunger in the press, turn it upside down, add freshly ground coffee, add your 200 degree water, let it burp and or stir, top off with water, put filter in place, screw on plastic strainer, place right side up over cup using the hex to circle converter toy and let sit for a few seconds and press.
Everything is variable and you will find your preferences for amount of coffee and brew time quickly enough. I think I aim for about an inch of ground coffee and maybe a minute or so from water hitting the coffee to being pressed out.
I had pic's of this about a million years ago. Will post again if needed ... just for you, Barry.