I am too lazy to prepare the buffer myself, and here is a slightly mofied version.
A) 2x mix:
NEB buffer 4: 160 ”L
Glycerol: 1 mL
NEB 10xBSA (10 mg/mL): 840 ”L
B) dilute Exo III (NEB M0265S) 1 in 100 with A
Mix 1600 uL of A, 2 ”L of B, and 50 ”L ExoT (NEB 2170A)
about 1 year ago