Installing facia on my layout, the Trenton Subdivision in N scale. I’m using 1/8 inch mahogany plywood screwed to the cross bracing. I have left room above the screws to attach a removable plexiglass shield.
 

My old hospital table has proven to be invaluable. Using a clamp to secure one end of the facia I can adjust and hold the other end at the correct height while I drill the holes and secure the screws. The table also doubles as a bench for my tools.