I’ve heard of spraying “Pam” on the whole thing. I tried it with a fondant decoration before placing it on the cake. It worked really well, looked steamed. If you use this method though, know that the shine will go away after about 24 hrs. I guess the spray get’s absorbed.
Alcohol like vodka and a paintbrush do work well for touch ups too since alcohol drys faster than water. I have done the shortening technique myself and like it too just make sure it’s evenly applied. Someone mentioned (i think it’s jessicakes blog) using a piece of fondant, roll it into a little ball and touch it on the cake where cornstarch is. I haven’t tried it yet it sounds like it works good for her. As far as the steamer goes I think most of us saw Cake Boss do this. I bought one myself last year to try and it became very addictive for me. I agree I don’t like the wet look and I have some pictures of cakes that do look wet cause of this. I did find that if you do it lightly it really does help the colors pop and it can dry back to normal and not look wet (can take a couple of hours though).