This is the stuff I use - Kester 66/44 .8mm. Looks like it's 20% off right now, $30, pretty good price. It's not nearly as messy or sticky as some of the other stuff I've used.
https://www.amazon.com/gp/product/B001W2XZOS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1