So over here the author recommends C511 solder:

Once you find a good brand of solder that flows smoothly, doesn’t make a mess, and gives you excellent joints, you don’t easily switch to something else. A spool of C511 solder isn’t cheap, but it offers amazing quality. I’ve been forced to use cheap solder in the workplace before, and usually end up taking in my Loctite solder to use. Some cheap solder flows like mud or has flux that makes a huge mess on your board. C511 is a no-clean solder that is an RoHS compliant Tin/Silver/Copper blend. You can get it in a range of diameters; I’ll typically have a roll of 0.56mm and a roll of 1.63mm on hand. The 0.56mm is good for fine pitch components, and the 1.63mm for tinning thick wires or large components.