Hi Grace,
I have a Christopher McClean/McLain, Gunsmith who appears in the report to the Fictitious Votes Committee in Dublin in 1837. He had the vote because he had been admitted to the Ancient Freedom of Dublin on the basis of 'service' (his smithing apprenticeship presumably?). His father, a blacksmith, had also been admitted in 1802 on the basis of 'service'. This doesn't tell you any more about the apprenticeship - but the Ancient Freedom Records may be another avenue for research?
iem