My current jar of cheap ebay stuff, it's like rosin mixed with wax. Trying to solder with it, well it's pretty weak stuff so it's lousy, but rarely have to worry about shorts with it. So anytime I have to work on SMD IC's, or something I can't easily clean, I use this.
The other stuff I use, MG Chemicals 8342 RA rosin, it's great for eating corrosion and wetting, but it has to be well cleaned off afterwards. There's not much issue with large solder balls, but it can leave a conductive residue, and it spits and crackles everywhere. I've had it get under traces, and mess up a PCB I solder on too many times.
On PCB's or protoboards, if I really want them clean, I use a toothbrush, ISP alcohol, and then soapy water. But yeah, I'm afraid too use that good stuff on chips and certain SMD stuff. I need to find something in between.