How do you get a dry surface on gummie candies?

I made this recipe for sour gummies:

Gummies

• 2 C / 473ml fruit juice (I used apple)
• 2.5 C / 600ml water, divided
• 4.5 tsp citric acid
• 6.6 oz / 187g gelatin
• 22.4 oz / 625g sugar

Coating

• 6 T sugar
• 3.5 tsp citric acid

[I’m skipping the actual cooking of the candy, which is not relevant
to my question, and going straight to the final step.]

Toss the pieces in the sugar-citric acid mixture and place on the
cooling rack.

Let the coated candies dry for 8 hours on the cooling rack until the
coating is hard and crunchy.

The coating did not in fact become hard and crunchy: it became slimy and sticky. The only remedy I could think of was to toss the candies in corn starch. That worked (the candies aren’t crunchy, but they’re also not slimy, which is what really matters), but I’m wondering whether I should have done something differently the first time around. Is there a better way to make gummies with a dry surface (that’s practical for a home cook)?