Guidelines for the full synthetic conjugation can be found here:
traditional conjugation and dialectical differences.
In the Munster Irish I learned, the only analytic forms to be replaced with synthetic ones would be the second-person singular (
ceiliúrair for
ceiliúrann tú) and third-person plural (
ceiliúraid (
siad) for
ceiliúrann siad).
In this case, I doubt the second-person synthetic form would ever be used because of the awkwardness of pronunciation. The reason for the pleonastic
siad with
ceiliúraid may be that there are other synthetic forms where the ending is pronounced /əg'/ (e.g. the second-person plural imperative
ceiliúraidh).
It's an odd verb in any case, isn't it? Normally polysyllabic stems take the endings of the second conjugation.
