In addition to the above, I can suggest a few tips that help me do a better job, that you may or may not be already using:
- Typically work in an environment with fewer sources of dust (it helps to close the outside street doors, avoid carpets, curtains, certain types of garments.. I work on a clean wooded surface in a sort of cubicle to avoid drafts, etc.).
- When removing the LCD from the iPad, I most importantly try to avoid leaving any smudges until I have stored it away in a small dedicated drawer. If you didn't put it there in the first place, you won't need to clean it! I rarely wear gloves since they get stuck on the glue. I'd rather control how I gently and lightly I hold the LCD from the edges and the bottom. Now it is second nature..
- If I do smudge the LCD, I don't try to clean it. I just leave all the cleaning to be done in one time at the very end. Otherwise you risk spending way to much time doing repeated cleaning.
- The LCD and digitizer are the last things in. Meaning I clean the aluminum casing, straighten any edges that need it, apply the double-tape, air-blow the iPad using a dust blower to remove dust and particles, then finally re-install the LCD and digitizer.
- I try to avoid any contact with the foam on the edges of the LCD since it tends to break into small pieces. Trying to wipe them off is a big mistake since they will sort of smear on the surface. Use a dust blower instead.
- Once the LCD is screwed back in space, I:
-1- Use the dust blower to blow any particles and dust away from the surface of the LCD,
-2- Use a lint-free / micro-fiber clothe to very lightly BRUSH AWAY any particles that the blowing did not remove, NOT wipe them away if I don't have to. Wiping may lead to smearing..!
-3- DRY-wipe any finger print or smudge,
-4- Repeat 1 and 2,
-5- Remove the double-tape top stickers using tweezers, as well as the inner protective nylon sheet typically found on the new touch screen, and repeat 1 and 2 again.
-6- Immediately glue the touch screen in place to avoid further contamination.
The above may seem a long list, but it actually takes just 3-6 minutes to do steps 1-to-6 once you get the hang of it.
- Brushes may leave bristles that show up after closing the iPad (Murphy's law ;) ). I never use them.
- I don't use cleaning agents, they tend to leave marks as you observed. Wiping lightly and repeatedly using a dry lint-free micro fibre clothe is the way to go in my opinion.
- Someone suggested using cling film to protect the LCD. Tried it, it left marks that were hard to remove. May be I used a bad quality?
Good luck and please share any additional tips you may have..