Up until now I have been buying solder flux bottles and put it on the pcb with cotton swabs. Unfortunatly parts of the swabs coma loose and entangle themselves in components. In addition to that it felt kinda wrong to use cotton swabs to put the flux on. That’s why I’m switching to solder pens now – and compare three of them in this post,
These are the pens I bought off ebay. The number in the bottom right corner helps identify them in the upcoming rating: