"It seems that verbal morphology is one of the most important reasons why Ulster speakers tend to shun the current standard language. We already saw that the typical long ó in the future and conditional of the second conjugation of verbs tends in Ulster to manifest itself as [ah] in pronunciation, a fact that supports the old orthography -óchaidh, -eochaidh, -óchadh, -eochadh, for this kind of inflectional endings. Besides, these endings tend to spread to first conjugation, especially to frequent verbs such as féach-, amharc- and so on. However, there are other features requiring attention, notably the intrusive long ó’s in future and conditional."

How prevailent is this feature? Could I say crúóidh mé? I don't know if Donegal likes diphthongs like this, even if they are just evinced in verbs based on changes (seems like Cois Fhairrige would prefer them more). Anyway, would they be an understadnable way to speak?

I don't think one would say crúóidh mé. There are some verbs that are in the 1st conjugation in the other dialects and that are in the 2nd in Donegal, but not many, as far as I know. People say amharcóchaidh, druideochaidh, fanóchaidh...