I've followed an advice about studying stress marks. I find very elegant putting all the breves and macrons. But, in differents dictionaries several conventions are used. For example, the word consŭl, I have found this word as consŭl and consul. For myself I write this word as Cŏnsŭl, because the letter "o" isn't long I suppose is short, then I put the breve sign. Is this correct in general (or at least in this case)?
In most cases, there's a distinction between short and long vowels in Latin. But in a few specific environments, that distinction is neutralized—short and long vowels are pronounced exactly the same.
One of those environments is before NS or NF. It seems likely that the combination of vowel and N in this environment was pronounced as a long nasalized vowel; this is why "consul" is abbreviated as COS instead of CON.
In other words, the words cŏnsŭl and cōnsŭl would be pronounced exactly the same (with a long nasal
[õː]). As a result, most dictionaries don't bother to mark length on vowels before NS and NF; it just doesn't matter.