Deffo on the flux paste, I use fluxite soldering paste and 60/40 solder and a portasol technic gas powered soldering iron and I tin the wires and the motor tabs with the paste and solder, then put a bit more flux on both and solder together, it takes in seconds and creates an excellent strong finish,
http://www.ebay.co.uk/itm/FRYS-FLUXI...2#ht_500wt_969
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i've had one of these 50g tins for 20 years and i still have enough for a few years yet, and i solder a lot and use it every time, great investment