On this RCM fix...do I want to completely melt away the old solder or just add new solder on top of the old? Do I heat the pins on the board to draw in new solder or just heat the solder and let it drip onto the contacts? Is resin core solder the same as rosin core solder? Sorry for all these questions...I' m just ' detail' type of person. Thanks in advance for any info on this.