Installing windowpanes into a brass Milwaukee Skytop Sleeper Observation

Hi folks

how would you proceed and what material would you take for installing windowpanes into an empty H0 scale brass Miwaukee Road Skytop Sleeper Observation by Soho??? I mean the lounge area at the rear of the car is really tricky, so I don´t have any idea yet how to install good looking windowpanes. Any tips? That would be great!