From my experience unless you can outline exactly what's in it for the blogger personally or his/her readers - cold emails are useless. What could be the right

From my experience unless you can outline exactly what's in it for the blogger personally or his/her readers - cold emails are useless. What could be the right incentive? Exclusive data (for bigger blogs), early access, promo codes, discount codes, free subscription, valuable content as a guest post, the list goes on. Just asking for review regardless how cool is your project is not enough.