Don't worry about rough edges or whatever on things like your buckle. For your first casting job it looks really good, and will fit the bill nicely. I always follow the "3 metre rule" of cosplay, which states that no matter how many inconsistencies and rough parts you can see up close because you MADE the item, if it looks good at about 3 metres then it's fine because that is about the distance that most photos are taken from at cons

. Besides we're always our own harshest critics, I know myself I always see problems with my own work that other people either don't see or don't think are an issue. As for the paint remaining tacky, that could have something to do with humidity or the place you are painting them in. Maybe trying putting either a matte or gloss clearcoat over the top, depending on the type of finish you're looking for, and see if that gets rid of the tackyness?
Good luck with your build, I always enjoy seeing a good Black Widow

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