I guess this is kind of old news, but there is an OPI Spotted dupe being sold at Walmart by a company called Fing'rs. I was able to buy one, and a bunch of other things they have for nail art too, recently. This is my review. I've seen a bad review and a good review. Luckily mine worked out great so this is going to be a pretty good review as well.
I didn't use thin coats and I didn't use thick coats. I tried to just have a normal amount of polish on the brush as I would use if it was normal polish (did that make any sense?).