[dsraven]

-prep both sides of the metal all around the holes to eliminate contamiated welds-get rid of oil and grease or wax/silicones(first), paint, rust, etc.

-fit filler pieces and ensure they are also clean bare metal on both sides. tack weld the fillers into the holes so you are sure to get the right plug for each hole. some guys will use magnets to hold the plugs in place while they tack weld. I find magnets distort the "field" around the mig welder (if that is what you will be using) so as soon as they are tacked in the magnets go away. I am sure your welder guy will have his own method but maybe stick around so you can be the "inside guy" to assist getting the plugs nice and flat in the hole when tacking them in place. a nice piece of flat material would be good to have kicking around to hold against the plug from the back side and keep it flat. a spare welders helmet would be an asset for you. wear long sleeves and a tight neckline, welding is like standing out in the sun on a mid summer afternoon, it will cause sunburn like reaction. NEVER LOOK AT OR WATCH THE ARC WITHOUT A SHIELD. you probably knew that already.

-weld in filler pieces leaving time for areas to cool off. don't overheat the area by trying to weld the whole plug at once or by welding a bunch of plugs all in the same area. weld all over the place a bit at a time so one area doesn't get hot and distort. take breaks to allow cool down

-grind the welds smooth. check for anything that looks like a pinhole. a bright light on one side with a set of eyes on the other side will usually find anything big.

-hammer and dolly, shrinking tools as required to get the spots as flat as possible.

-sand and feather out any areas that lap out onto the paint.I use 80 grit at this point because it roughs out fast. this will save you steps later. downgrade to a higher number once it is roughed in

-seal with epoxy, then use filler as required. when good respray with epoxy. when epoxy has flashed off or is ready to coat over (see directions on the can) spray with high build primer (primer surfacer, ask the body supply guys which ones are good for easy sanding, I hear slick sand is good for fast sanding and no paper plugging) and block sand. repeat the high build primer and sanding routine until no low spots are left and it looks good in the reflection of a light. I usually wipe the area down with a super wet rag of wax and grease remover, with a light shining from the opposite direction, so I get a good reflection of light on the surface. I find this way simulates you seeing it like it will be after a fresh paint job. if you see a bump now you will also see the bump in the fresh paint.

-some guys will use a fiberglass filler initially to fill any pinholes not found with the light. regular filler is porous so it will allow water through and start the rust process right away. spray a good coat of epoxy on each spot as well to ensure a good penetration into anything that may even think it is a pin hole.

take pics as you go for your memory of where stuff was. post up some pics of the progress