Obviously this is something you really should do as sMerit is basically useless to hoard. I would recommend you to give it to any post that you think is good and quality regardless if it is in your local board or up to you.

Then, you don't need to mention everyone especially merit source who have helped you to get merit in multiple thread. Some of them might think you're begging at the mention, but only they know exactly. Contribute to the community, it's a way of thanking that is actually expected after you have successfully rank up with the help of these people. Good job from you man, keep it up.