After your job is completed, there is really only one rule you have to abide. DO NOT TOUCH IT FOR 4 WEEKS.
At the factory when headliners are manufactured. The headliner board comes out of a machine that made it. They are then put away for 2 weeks to cure before they are installed by a robot. We do not have that luxury in a real world situation. Road Show Chris has to install the board uncured. After 4 weeks you can touch it. During the 4 weeks it could be touched ever so lightly but if pressed into will create a pressure indent that may not come out. There may be a glue smell as well. This is not harmful and will be gone in a day.