Green’s Dictionary of Slang

(Irish) to smarten up, to dress up, to dress fashionably; thus blemmed (up) adj.; blemming-up n.

1972		(con. 1940s) N. Conway Bloods 36: He’d still have hours to kill after he’d finished the blemming-up. [Ibid.] 124: The cap badges [...] must never be blemmed because they’d always have to stay black as a sign of perpetual mourning for Michael Collins.
1987		(con. 1920s) L. Redmond Emerald Square 95: To wait, with a pile of sods, for some grown up ‘jazzers’ [...] who, all blemmed up, were heading for the Fountain Picture House in James Street.