Hello,
It's nice to look on the bloggers website and articles if they wrote something about crowdfunding or kickstarter. It's always good to keep your message little bit personal so they will know you are not just another spam.
Try to find blogs or websites that are intersted in products that are similar to yours or blogs that are interested in new gadgets, design or they are writting a lot about problems you can solve with your product.
As 'Women in Blues' wrote above me, you are asking them for a favour, so It's always good to offer them something what they could be interested in. Like you can send them your product, so they can try it and make review or you can offer them place on your website as thank you or someting like that .
I hope it will help you. Good luck and have a nice day
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