Many that are powder paint are not only closed, they are not cured well if at all. Vinyl doesn't do that though and actually is a little tougher coating that Powder, but it's time consuming since they have to dry for a while!
I have some close on me during the cure even though I use my trusty tooth pick thing to open after the dip, but some I guess have too much paint and close back up in the cure. For these I use a bodkin that has a thinner needle than most and I heat it and stick it through and wiggle from both sides to open it well and try to clean off any sharp edges from the paint. It's a bit frustrating, but since I have been doing that for I guess 12 years or so, it works for me even if it does slow down my tying a bit.
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