You will need a cable needle.
You will need 5 buttons. Rowan used #BN1709/15 from Bedecked in the UK.

Finished measurements:
Chest circumference: 20.75(22.5, 24.75, 26.5, 28.5)“ 52.5(57, 63, 67.5, 72.5) cm
Finished length: 20(20.75, 21.75, 22.5, 23.25)” 51(53, 55, 57, 59) cm
Sleeve length: 17(17, 17.25, 17.25, 17.25)“ 43(43, 44,44,44) cm

Yarn used:
Rowan Alpaca Soft DK
Shade 218 Brick - 10(10, 12, 13, 14) balls