OK, yeah, the brown dots are probably that flux you've added. You might find it a lot easier to use a 60/40 leaded solder with rosin core flux in the solder, then you don't need the separate bottle of flux.
The Fluitin 1532 solder is a rosin core solder. "DESCRIPTION - Alpha Fluitin 1532 is an activated rosin cored solder wire developed for general hand soldering applications. Fluitin 1532 is suitable for use in any commercial no-clean hand soldering application that specifies compliance to J-STD-004 – ROM1 standard." It's pretty standard useful stuff. There was never a need to use flux from a bottle.