be a dab hand at something/at doing something
be a dab hand
To be skilled in a particular area. Primarily heard in UK, Australia. Amanda can fix that hole in your blouse—she's a dab hand at sewing.
be a dab hand atbe expert at.
Dab in this sense is recorded since the late 17th century, but its origin is unknown.
1998 Bookseller Stephanie Cabot…is apparently a dab hand at milking cows, according to one of those mystifying diary items in Skateboarders' Weekly.