Lisa, I wear many which aren't full button-downs. Most of mine aren't. I have about 15-18 modified shirts. Some are shirts with just two or three buttons up top, or ones with a beaded neckline. It helps since I don't always mount my camera front and center, depending on the shop. Car shops, for example... personally I've had bad luck with always being able to face my target head-on, as they're normally demonstrating something or standing more to the side of me, than in front.
Like this, but with more beading.
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www.ebay.com]
My husband has a few like this. Personally, I try to pick things which have a busy print or a busy... something... going on, but he prefers plain and simple.
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www.ebay.com]
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Plan the work. Work the plan.