For those having smoke shadows and not only dust, you can go further than 90° and open the 2 parts like a book as he did in this vid :

https://www.youtube.com/watch?v=1rGBpCIQ...

Simply be very careful when you lift up the LCD there are plastics at the bottom (where are the connectics) which could damage the LCD when you open it so simply take the LCD though the edges and raise it a little bit when opening it up.

Personnaly I did it on a bed and it worked perfectly.

Then use some glass cleaner on both LCD and Backlight to remove the smoke residue and be careful to leave no traces