When i first learned concertina, Alistair Anderson stated [if i remember correctly] that slip jigs 9/ 8 have an emphasis on first fourth and seventh beats .so worth experimenting with changing bellows direction where you want to emphasise. so the first bar of drops of brandy has 3 groups of 3, try changing bellows first fourth seventh.
   irish mazurkas , which are written in 3/4 there is supposed to be an emphasis [as i understand it] on the second beat to achieve this i would change bellows between first and second beats,