I just did inner and outers on my 89 in January. Don't tack anything until you have all the parts fit up and the door checked. The guy in the video needs to put the welder away until all parts are fit to the door.
Clamps, visegrips, or even a self tapper or two can be used. Get all pieces fitting right, check the door for fit and then you can do some tacking. Keep checking door fit as you go. I fit all mine then welded the back of the inner, blew it apart, dressed the welds and epoxy primed. I then fit the outers, again checked the door, welded what I could, dressed those welds. epoxied under the cab corner, fit the cab corner, checked door, welded cab corner, blew it apart, finished welds up front, dressed welds and moved on to the "paint shop".
I added an extra 1 1/2" hole in the backside near the cab corner to get rustproofing in, A plastic plug in the hole allows me to add more in a few years.
You are using aftermarket panels you will need to massage them to get them to fit. I had OEM and still needed a few adjustments. It is metal, you can cut, bend weld etc.
