Does Dewgong's "Dual Blizzard" attack let you do 60 damage each to two separate Pokemon, or does it do 60 total damage split between the two any way I like?
It does 60 damage to each of the two Pokemon separately. And don't forget to apply Weakness & Resistance where applicable.
Source: Unbroken Bonds FAQ (2019-04-19), TPCi Rules Team (2019-05-02)

Relevant cards

Note: All applicable cards may not be listed below.
SM10_45
SM10_45