Old french is very phonetic. That's why you find so many spelling for the same word, even in the same text.
Additionally, the texts were written to be declaimed in public, repeated from crieur(!) to troubadour. So prosody was significant.
Froissard would not have bothered to write, especially the Chronicles, in vulgar,
as opposed to latim, much more easy to read and write because standardised, without a very good reason. It was the Royal propaganda directed to a public which was unable to read, before TV and microphones. So you can be sure that the prosody (rhythm, stress, intonation, music,...) was well studied and gives every possible indication about how and what to read.
The best way to grasp old french pronunciation is probably for you to take a small part of a text/poem, try to find out its music, put your tongue back in your mouth, and start chant it with neat stops between words. It is almost impossible to read it wrong!
*Là, fut un mons et un tas de Flamands occis, moult long et moult haut.*
moult-e long é moult-e h-a-ou-l-t -- how could it be otherwise:
If long [<longus] et haut [<altus] have the same phonetic envelope, then haut could not be the single o it is today. It should start with something strong, hence the h which was audible. And the au did not yet merged in a single phoneme but was a sliding diphtong. Note that the L was pronounced from the far back of the mouth, like in Portuguese, and was sounding like a u [cf. un cheval[-au], des chevals[-aus]], hence alt>*hau(l)t* and mult>*moult* [> modern, mou].
With such a sounding sentence, nor time nor Chinese whispers could never make to forget the Flemishs were killed by the King, in big lots, and all big guys.
You can check in the introduction of modern editions of old french texts where they explain about the specifics of the pronunciation, grammar, syntax specific to the text/author/period/dialect. You may not find the exact word your are looking at, but you will be redirected to similar cases from which you can generalise.
You will also find useful to consult dictionaries and word indexes. They usually mention variants inside and outside the text. Remembering the spelling was not random, and that the reference was the speech, not the written like today, these will give you as many indications about the way old french was spoken.
But the guide you will find are very general because, as a matter of fact, old french is an accurate phonetic transcription.