I bought the Wilton number pans, I'm making the numbers 61. My question is if I don't ice the cake fully, how do I keep it from drying out? The icing will only be in between the layers in big dots and on the top layer, sides will be fully exposed. Would a simple syrup brushed on the sides keep it from drying out?

I would use a simple syrup, and I might even make sure that the customer knows that with any type of exposed cake, there is a greater chance for it to dry out, and that it should be expected, even though you’ll do what you can to prevent it.

what about a glaze?

I’ve used clear piping gel 

Oh, I love the idea of piping gel!