How would you say "My father is a bullshiter"??
I'm guessing it would be;"

Is gobshite m'athair

or would I need an extra 'é' on the end??

You know gobshite is an English word right?

https://en.m.wiktionary.org/wiki/gobshite

Can you clarify what you mean by bullshitter?

B’fhéidir:
Breallaire é m’athair.
Breallaire is ea m’athair.

in ionad breallaire:
buimbiléir, glagaire, glagaín, liopaire, prioll, raiméisí, agus araile

Donegal: Is breallaire m'athair ; breallaire m'athair ; breallaire atá in m'athair

_________________
Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

How about - Cac ar oineach is ea m'athair ?

and there's this -

www.focloir.ie/en/dictionary/ei/shite+talking