well here it is again the age old question.where is the best place to start drilling spot welds ?and where are they all located. thanks again

When I did full quarter and outer wheelhouse replacement on my car two years ago, I used a wire wheel chucked in a drill to remove the old paint, seam sealer, and whatever else was on top of the spot welds to expose them. Most were easily seen as it looks like the pinchers on the spot welder tongs really had to clamp down to bring the two pieces of metal together while others there were only faint marks left in the metal.
For some reason I tried taking the whole quarter off in a big section but others have cut the big parts off of the car with a jig saw or sawzall and then come back to work at removing what's left. If I ever do it again, that seems the better way to do it.
Most of the spot welds on my car were removed using a cutoff wheel in a die grinder to thin down the metal on the spot weld so I was left with a solid lip on the part. This would give me a nice undrilled solid lip to reattach the new metal onto. I did though have to drill out some spot welds but there were not that many. I never did try the spot weld remover drill bits but used the stepped drill bit called a "Unibit".
After I got the old metal off I came back with a hammer and dolly and straightened the lips on the car so the new panel would fit the best it could.
I also would wedge a screwdriver between the old panel on the car that was to remain and the section that was being removed and it seemed easier to locate the spot welds as the metal would bend but only to the next spot weld.
To reattach the new panels on my car I drilled some 3/8" holes on the lip of the new part or on the old part depending on how I could get in there with a wire feed welder and then clamped the two pieces together close to that hole and then plug welded the two lips together and filled it up with weld. After I was done I ground them all down and then put on a primer and top coat over them to keep the or slow down the rust from forming.
I had never done large panel replacements before but I found out that time needs to be spent by putting the parts on and then taking them back off so they can be fitted and adjusted to fit the best that they can and then slowly start welding them on while checking that the door, trunk lid, etc, still fit nice up against the new panel. If you spend this time and not try and rush through it, you will get it to fit and look better than how it was originally.
Jim