I can think of quite a few electricians here on this forum (including myself) that could and would be able to find the cause of your tripping RCD problem, and it wouldn't take them a whole day to do so either. No they are not ''superhuman'', and it's not rocket science either, it's just a matter of knowing what they are doing and why. There is nothing out there, that can take the place of experience. That experience combined with methodical intelligent fault finding, will ALWAYS lead to the fault being found, ...or at least to a localised location where access is severely limited!!
For someone that claims to conduct as many rewires and the like as yourself, how the hell have you got by without a leakage clamp in your test kit...
May i suggest this model from our forum sponsor, that has specifications equal too or better than other leakage clamp meters available at much higher costs. You'll also get a 5% discount from our sponsor too!!
TM-EL9809 High Resolution AC Earth Leakage Clamp Meter