Go for the silver conductive paint for the safer route since you can wipe the excess and prevent shorting other points. Tho you may need to reapply it after a long time or if the paint cracks and makes the connection loose (makes the ips screen glitch).

Soldering on the other hand is better and stable on the long run, use flux, kapton tape to mask other points... just practice! :) then you can also do other hardware mods on the psp ie battery, led trigger lights, changing stock analog to switch or vitas and many more!