You’ve probably seen some of the other free brushes around here (if not, look around!). Basically whenever I need a special brush I can make, I share it on here in case anyone else needs one and this can save you some time. This is Christmas Lights II, it’s black and white, and this time includes both inside and outside corners. Don’t let this leap in features fool you, it’s still a pretty basic brush, but maybe you can use it, or, I’ve included the sources on the page, so feel free to modify or build on it. I hope you do something cool with it.
https://jeffco.ca/blog-content/christmas-lights-ai.zip
And check out other free Illustrator and Photoshop brushes by clicking on Free Stuff.