Those hydraulic crimpers are pretty nice. You just need to be 100% sure that the dies really are the size they claim to be. Some of them being sold are metic sizes and they've just stamped the nearest AWG size on them. Fine for hobby use, but it won't cut it when you start pulling a few hundred amps through the crimps.
I have a contractor that does some of my big installs for me. He has a really high end hexagon crimper that will do all the way up into the MCM size cable range. He's done 350MCM size crimps for me on our big battery systems. I think when he bought the tool back in the early 1990's, it was somewhere north of $5,000.
For most of what I do at work, up to 0000 is good enough. So I have two sets of crimpers that will do everything from 8 gauge up to 0000.
At home, I have the Thomas and Betts crimpers that do 8, 6, 4 and 2 gauge, which is plenty for me.
My good ones at work even stamp the crimp size on the lug, so theoretically they can be inspected after installation. I do the inspections, so I'm good with it.
There's good deals on the used market. Truth is, the manual crimpers really have little that can go wrong with them. Getting an old rusty pair and disassembling and cleaning will be a good investment. The last set I bought needed some TLC, but I've more than received my money back on the investment.
Sometimes you'll hear people try to discourage crimping and suggest soldering is the only way to go. Usually it's old hams doing this.
Soldering is fine if you can get everything hot enough. That can be difficult to do on larger cable/lugs. If you don't do it right, you can end up with cold solder joints that will fail. The other issue is that the solder will wick down the strands and make the cable really stiff right near the connection. That usually leads to failure in an environment where there is vibration. I've been told that aircraft installations do not permit soldering due to this issue.
A good exercise is to do a proper crimp on a piece of scrap cable, and then saw it open and inspect the inside. If done correctly, you'll have what they call a "gas tight" connection. In other words, the crimp is so tight, it's gas tight, as in no moist air can get inside and corrode it. It's considered a form of welding. The fine strands of the conductor all look like one, and you shouldn't be able to see the transition between the conductor and the lug.
The No-Ox-Id is handy since it fills in any potential gaps. When everything is crimped and torqued correctly, the No-Ox-Id will fill voids, but get pressed out of any metal to metal connections. It'll prevent corrosion and give you a trouble free joint. I do it on all our DC power stuff, as well as all the ground bonds.
I've never had one fail.
The adhesive lined heat shrink will seal everything from the outside. It serves the purpose of sealing the insulation to lug connection. It also makes the connection look really professional and provides some level of strain relief.
Some of my equipment is pretty close to the ocean, so taking these steps is pretty important.
