You DO NOT need to pay for any special cleaning fluids or alcohol-based solutions, just water, a clean cloth and a micro-fine cloth (very cheap).
My 'technique' is to use a new, very slightly damp cloth (just damp with water). You really want it to only be very slightly damp - it shouldn't be dripping wet or release any water when squeezed, just barely damp enough to leave a slight smear on the screen.
Then use MINIMAL pressure on the screen, as softly and slowly as possible, to wipe any marks. If dirt or a mark is stubborn, don't increase pressure, just continue softly/slowly and move across it in different directions.
When you finish, there will be smear marks on the screen (from the dampness). Then use a clean micro-fibre cloth to softly and gently wipe the smear marks away.
I've used this technique on every retina MacBook I've had and it works fine, never removes any protective coating or anything like that. Used tap water fine, cleaned the same MBP multiple times with it and it didn't affect the coating. It's more about the technique.
My 'technique' is to use a new, very slightly damp cloth (just damp with water). You really want it to only be very slightly damp - it shouldn't be dripping wet or release any water when squeezed, just barely damp enough to leave a slight smear on the screen.
Then use MINIMAL pressure on the screen, as softly and slowly as possible, to wipe any marks. If dirt or a mark is stubborn, don't increase pressure, just continue softly/slowly and move across it in different directions.
When you finish, there will be smear marks on the screen (from the dampness). Then use a clean micro-fibre cloth to softly and gently wipe the smear marks away.
I've used this technique on every retina MacBook I've had and it works fine, never removes any protective coating or anything like that. Used tap water fine, cleaned the same MBP multiple times with it and it didn't affect the coating. It's more about the technique.