[Kenwood] TS9930S through plates soldering

[Fortra]

Hi guys,

has two TS-930S with known cold solder joints on Digital unit. One 930S is 
s.n.307xxxx the second one is 80xxxx.
Have had done thorough resoldering on DU of s.n.307xxx once in the past. 
Simpthoms are that the through plating of holes 15,16,17 ( no digital 
display after turning the VFO), has to be resoldered.
Questions:
1.Any particular advice regarding technique of soldering and resoldering, 
quality of solder or whatever??

2.Did anyone of you experiencing similar problem in the past did all through 
plates resoldering by using bare wire through the plates adding new
contact ??

Thanks in advance, looking for the " cold solder night session"!

Regards, Nermin S58DX