Yes, I thought about the magnifier, but how would one do the soldering? Soldering each pin at a time? As those parts have 0.5mm or 0.8mm pitches, I only tried with this "drag soldering" technique, but with the aforementioned results.
I usually apply solder on 1 pad on the PCB, then hold the part with tweezers and place it while heating that pad. Once the placement is good, I solder the rest.
I tend to do them 1-by-1, not by dragging over the complete row. If the pitch is smaller than the iron tip, you don't have a choice and need to solder several at once, but usually with flux and the right quantity of solder it works itself out.
For the problems you mention, adding flux and reheating usually works. If there is too much solder, you need to wick some away.
