Quintessences

I see that some of the equilibrium bottles have been paired with particular recommended quintessences. What is the role of quintessences? Is it used daily at the same time as the equilibrium bottle...or only on an "as needed" basis? As a little experiment, I bought an equilibrium bottle from here, didn't look at the recommended quintessence, and picked a quintessence based on what resonated with me. Afterwards, I looked up the recommended quintessence...only to find that it didn't match with the one that I had selected on my own. Will the quintessence still be useable even though it may not be the recommended one paired for the equilibrium bottle that I bought?
Finally, would the quintessence still work even though I do not believe in any of these ascended masters from which these quintessences derive their names?

Quintessences play a supportive role to the Equilibrium, and usually aren't directly linked to the Equilibrium bottle being used. They are selected from the other 3 bottles by one of the master bottles or pastel colours being present, and if none are, then any Quintessence that resonates are appropriate. Sometimes, as you say, the qualities indicated by the Quintessence don't resonate with the choice, and it is best then to use the one(s) you feel resonate most with you at the time. They can be used at the same time as your Equilibrium, and also carried with you if you wish, to use during the day to 'clear the air ' and harmonise the energy field. Different ones may be used at different times on the same day, as preferred.

Quintessences invoke the potential of learning to master the qualities represented. There is no need to believe in the masters (teachers) they are named after. I prefer to think of them as archetypal qualities that were represented by teachers and mythologies of various traditions in the past, for example invoking peaceful communication and alignment with authoring one's script in life; invoking the awareness of consciousness in all of creation from the cosmos to the earth; invoking the qualities of unconditional love, self-acceptance and forgiveness etc. Generally these qualities can be found in the ancient wisdom traditions, even though they may be expressed in differing story lines.