That is not the quite exact procedure being used. If you follow the references in the paper, you eventually get to another paper that provides a full experimental reference. I've copied just the experimental procedure below, and provided the doi reference:
To a solution of 2,5-dihydroxybenzaldehyde (5.0 g, 36.2 mmol, 1.0 equiv.) in 170 mL CHCl3 was added Br2 (1.94 mL, 37.7 mmol, 1.04 equiv.) in 120 mL CHCl3 dropwise over 1.5 h.
After addition, the reaction was stirred for another 1.5 h. The CHCl3 solution was then washed with 8 × 100 mL sat. Na2S2O3 to thoroughly remove excess Br2. The organic phase was dried over MgSO4, filtered, and the solvent removed in vacuo to afford 7.4 g (34.3 mmol, 94%) of 2-Bromo-3,5-dihydroxybenzaldehyde as yellow solid, which was adequately pure for characterization and used directly in the next step.
1H NMR (400 MHz, CDCl3) δ 11.63 (s, 1H), 10.24 (s, 1H), 7.21 (d, 1H, J = 9.2 Hz), 6.89 (d, 1H, J = 9.2 Hz), 5.39 (s, 1H); 13C NMR (75.0 MHz, CDCl3) δ 197.1, 158.5, 145.8, 125.7, 118.8, 116.7, 112.1; IR (thin film) νmax 3281, 1634, 1457, 1286, 1170 cm-1; CIHRMS M+ calculated for C7H5BrO3: 215.9438, found: 215.9422.http://dx.doi.org/10.1021/ol0159367