There's a thin (I believe 1/8") plywood that's made to go over a sub floor giving you a clean, smooth surface to lay your new flooring on. If it were my floor, I'd look into that instead of fooling with the existing glue left by the previous installation.
It's 1/4" thick, not 1/8".
If you do go that route do not use lauan plywood for many reasons!
You need to use what's commonly called multiply underlayment.
Do not use any glue!
Make sure the seams do not line up with the seams below.
The fastest easiest way to nail it down is with a pneumatic narrow crown staple gun.
It needs to be nailed every 4" on the edges and from 6 to 8" in the field.
Any gaps at the seams and any flaws need to be filled in and sanded.
It's in an older manufactured home. The vinyl flooring was glued down and has a foam backing. Then they installed indoor/outoor carpet onto the vinyl with some type of glue that is very sticky and nothing I've tried helps. I wondered about installing FloorMuffler Flooring Underlayment to the sticky stuff and install laminate flooring?