Hi,if this is still of use to you as your post is mnths old.
My cat gets &5 75 mcgm/hr Durogesic
transdermals a week.There are various meds which will dry your your mouth out.Good smoke being ideal.Research the others.It makes a huge difference if you are virtually non-salivating.100$ contact with membrane and no loss in the saliva.
A simple tip,just put on inside cheek,lie down with the patch cheek on the "upper"side of head/body and lie in foetal position.And excess saliva will run away to bottom cheek and be swallowed of ignored until theres too much.
Cutting a square of exactly the right fit,or even a circle,although this leaves hard to use pieces,is most important too..My Cat has legit script but will cheek a 1/6th or 1/4 of 75mcg/hr Durogesic transdermal(well 5 X75mcgs/hr a week).Real coffee
can make the mooth dry..iam sure many other meds,foods and suchlike will too.My Cat usually dosn find much issue with excess saliva !