I NEVER use soldering paste unless I'm soldering copper pipe or a radiator and even then the paste I use is acid core which should NEVER be used on electronics. Rosin flux is the paste you would use for electronics.
Flux core solder has more then enough flux to make a quality joint. I've been working with electronics for 25 years and there's no need for paste. I think I used it back when I was 5 years old and didn't learn to solder yet. =)