Rats with respire issues need to be medicated for at least 6 weeks. Otherwise they will not be better and the symptoms will return.
Baytril + doxy is frequently used, Baytril + azithromycin (10 mg/Ib) works very well. These meds are all given orally, twice a day for at least 6 weeks.
While it is true that there is no cure for myco, the flareups do need to be treated.
A tiny piece of dark chocolate can be used in emergencies to keep an airway open to give you time to get your rat to a vet. It is not a treatment for myco and I would caution against using it as a treat as chocolate is not good for animals (sugar, caffeine etc)
Humidifiers are good to use if the air is too dry as it helps rats breath better - I believe the optimum humidity for rats is 50% ..... but using a humidifier is not a treatment for myco.
Putting a rat in a steamy bathroom in a cage is a dangerous idea. When rats are having a difficult time breathing, taking them into a steamy bathroom may help them to breath.
However if your rat has fluid in it's lungs, going into a steamy bathroom will make it much harder for your rat to breath (the rats lungs have fluid accumulating in them) and your rat will panic because it can not breath.
If your rat is struggling to breath and you take it into a steamy bathroom, you will want to hold it and comfort it so that it does not become more stressed. You will also need to closely monitor your rat to see if the steam is helping or making things worse.
Taking your rat into a steamy bathroom is used in emergency situations to try to help a rat that is struggling to breath to be able to breath easier. The rat needs to be on medication from the vet as stream is a short term solution to help your rat breathe easier.
As mentioned by others, ammonia is not good to breath in and a clean environment is very important. Ammonia from a dirty cage, cig smoke etc can worsen myco flare ups.
Rats urine mark their territory (including their sleeping areas) and I have had many rats that like to "marinate".
Rats do not normally have difficulty controlling their toilet habits when sleeping - if that is happening there may be a health issue (see a vet) or a mobility issue (ie elderly rat with hed).
Myco commonly causes pneumonia, lung abscesses, emphysema, lung lesions, and can cause inflammation and bleeding in the uterus. All rats are assumed to have at least one strain of myco. ( a clean environment, good diet, low stress, and medical treatment at the first sign of illness are important.)
This is the first I have heard of mite prevention sprays being used with rats. Over the counter treatments and medications found in pet stores etc are frequently harmful to rats and may kill them. I would think that using a spray around rats would be unhealthy given their sensitive respiratory systems.
Kitten or cat Revolution (available from your vet) is the treatment for mites in rats.
There are many reasons for rats being itchy such as dry air, diet, allergies, etc. however, the first thing we try is treating with revolution for mites.
I hope this information helps