finding a short to ground and light issu

I'm trying to wire up a 1968 bug at work and it has some issues. First, a couple of lights seem dim but I bet that's a bad ground or bulb and haven't gotten to that but the rear tail light doesn't come on right away, and it takes a few minutes for it to come on. When it is on the voltage is adequate. I imagine this is on the (+) but is it a short? Seems like bad connectors maybe?

Also goofed up cause I plugged the wrong plug into the ground for the parking lamp while POWERED and a fuse blew and now it's blowing every time. DOh! Is this a short to ground? I have tried a continuity test to find it but I don't even know what's exactly on the circuit so I'm guessing it will show me continuity if I haven't unplugged all the loads/sockets? Maybe I'll do that now that I just learned what's on the fuses.

Last question. So I'm looking at this wiring diagram and it makes sense after looking at it for a while but it doesn't show me where these are located in the car. Is there something I'm not seeing. Are those numbers over the wires (2.5,1.0,.5,etc...)some sort of location ID? Is there something I have to get ahold of find where these wires are?

Sorry for all questions. I'm a bodytech and am getting the chance to mess around with electrical and it has been really fun reading up on it but finding the actual problems seems to be hard. Any help appreciated, thanks ahead of time.

Dim headlight sounds like a bad ground. Beetles suffered from one side being dim due to grounding (from what I was told). I think they may use ground switching (like some older Datsuns or Nissans that had the same problem.

If lighting takes a while, it sounds like bad contacts, not a short.

The fuse should only blow if there is a short - ie, pinched wire, or the wrong connection was enough to melt insulation or switch etc.   

The digits sound like wire gauge in mm (diameter).

Wiring should be straight forward - ie from the under-seat battery (with rear alternator) to the front. I think fuses were under the bonnet (to maximise the chance of exploding fuel tanks) and wire will go from there to the light switch on the dash. I don't know if the fuses are before or after the switch, or both.
Of course it is European wiring, and OLD Euro wiring at that, so it might not be that straight forward...
If it were mine, I'd replace the (ceramic?) fuses with newer blade types and use relays etc....

Fuse box was under the dash to one side, yes replace it, those ceramic fuses were lousy.
The numbers relate to wire gauges in ISO and are millimetres (mm).

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

thanks guys. I will print the schematic tonight for tomorrow. Sounds easy to you guys but it's kind of overwhelming. I'll post results.