Headliner cleaning

Sorry if this has been covered, I searched but couldn't find anything.

The headliner is out of the s10 as I wanted to check for roaches behind it.  It's not terrible but the contrast with the sun visors off is enough that it seems like a good idea to clean it while it's out.  

I have a can of tuff stuff I planned to use, it says spray on and wipe off with a cloth.  I added water (eventually powerwashing) while using this on the carpets and seats and the water really seemed to help pull the dirt out.  I'm guessing I don't want to get this type of backing wet?

Plan was to spray it down with the tuff stuff and give it a light scrub, then maybe mist some water on with a spray bottle while shop vac'ing to keep it dryish.  Should I skip spraying with the water?  Am I inviting headliner sag?

I'd be as gentle as possible to prevent the glue letting go. Use a very light touch. I wouldn't saturate it for sure but I don't see the harm in a damp cloth and lightly wiping it. I'd avoid the shop vac too, just follow up with a clean dry microfiber and let it air dry after that. 

Im not sure about the backside, but I've learned my lesson even using just a damp cloth to clean a few dirty spots.  I don't ever plan on even touching a headliner again.