Greetings Sir/madam.
I am glad that i may be able to help you to overcome your problem.
First of all i need to know the age of your father ? For what problem he has been hospitalised? What is his present condition? Is he conscious/ oriented/ bedridden? Can he be able to do his routine activity by himself?
It's unfortunate that your father is suffering from serious condition(telling this based on your details viz., ''cleaning mucus from mouth, applying dops to mouth, etc., '').

I am of the opinion that, (assuming your father is bedridden, unable to do normal routine work), he must be having excess mucus secretion from his respiratory passage getting stagnated in his mouth and air/food passage making him feel very uncomfortable with breathing difficulty.
If this is so the condition, then mucus secretion should be cleared routinely as and when it is collected with help of suction tube(ideally a nurse can help you).
If this is not done, it might end up little serious.

Looking forward for more details from you and provide further guidance .

Note:
Finally it's just a guidance. Not a definitive treatment as i haven't seen you personally. You've to realize that these are temporary remedies. We don't know what your exact condition is unless we see you personally. A doctor after personally examining you could help .

Hope i guide right & it helped your father.