I don't want to throw any bricks and any one method as basically the video link is a good way to square up a block assuming it's cut so that the aluminum welding wire will support the cut, if that saw cut was 1/8 off square the part will most likely lift on milling. Using 2,3,4 or more paper will do the same. On a part that small I would put something like a ball in the center. I would use 2 parallels or one with larger width so that the part not have be held while trying to clamp it. After getting one side flat I would most definitely us 2 parallels especially if the were wider. Also I feel the implication that something should be cut so that only one roughing cut is necessary is an over statement. Naturally we would all want to cut stock to size to avoid waste. However if I had a piece of 1 1/2 plate I'm not going to attempt to cut it smaller if I need 1". I would much rather cut 1/2" off on a mill than on a saw. I'm not sure where that block rough sawed aluminum came from but to saw that to size before milling seems like a lot of extra work. In my shop I have a lot of odds and ends, I'll select the nearest size saw if necessary but if I find 1 1/2 X 1 1/2 X 1 3/4 it will be milled not saw cut If I need a 1" cube.
Using digital calipers to measure .0005 is really stretching the capability of calipers. I wouldn't trust my Starrett to .005. I use a Micrometer for anything less that +/- .01 if possible. Removing and measuring and replacing the block, taking a roughing cut then a finishing cut is a gamble! I measure the part in the vise, measure after my roughing cuts and finish to size with out removing the part. After removing the part I remove the parallel , brush the vise clean, wipe the parallel and replace it. I can see the parallel rocking in the video.
Frank
Well Frank, you say that you don't want to throw any bricks, but then you throw them anyway.
I guess when I provided that link for the OP to help him visualize the technique I use for mounting work in a vise, I never thought that I would need to defend those techniques. But if you insist on throwing bricks, let's see if I can't deflect a few of them.
1) An aluminum wire works very well to fill the gaps between a rough sawn piece of stock and the vise jaw because it is soft and conforms to an irregular surface. I guess it probably wouldn't work very well if the part was sawed an eighth inch out of square, but my sister could probably do better than that with a hack saw so I think it's pretty much a non issue.
2) Using one or two parallels is a judgement call. Two are definitely the order of the day for larger parts, but for something as small as the block in the video, one works just fine.
3) I am a product of industry (over 40 years now) where time is money, and using one roughing cut and one finishing cut is definitely not an overstatement. I've worked for a lot of shops where milling a 1/2" or 3/4" off a part would get you fired in a heartbeat, in fact, I've seen it happen. Again, it's very easy to saw a part close to the finished size and it almost always saves time and money over extra time in the milling machine, not to mention the unnecessary wear on expensive tooling.
4) If you can't measure any closer than .005 with your calipers, then it may be time for a new pair. I would trust mine to a couple of thousandths even with a hangover. The comment in the video about it being a half thousandth off was apparently one of my mis-guided attempts at humor and I do apologize for that.
5) I have no clue what you mean by a rocking parallel.
I'm sure you realize that there are many different ways to accomplish the same thing in machining and whether they are right or wrong is pretty much meaningless as long as you end up making a good part in a reasonable amount of time and in a safe manner. These are techniques that I have developed over the years and they serve me quite well. If you have other methods, you should invest the time and energy into recording them for posterity (although it's not as easy as it seems). It's always interesting to see how the other guy does it.
Tom