Reddit mentions of IWISS SN-2549 Crimping Tools for AWG28-18 (0.08-1.0 mm2) XH2.54/Dupont 2.54/2.8/3.0/3.96/4.8/KF2510/JST Terminal Crimper Plier Ratcheting Wire Connector Crimping Tool

Not very. That crimper is made specifically for the PicoBlade series connectors from Molex. And at that, only one pitch of PicoBlade connectors (there are multiples) It will not work with all terminals in that range. Well, it might or might not but it's really a crapshoot. Molex crimpers are generally made for a specific set of terminals for a specific pitch for a specific connector series, and are not intended to be universal. Not sure if Molex offers interchangeable dies either, although I assume they would. BUT not all of their terminals use this style of crimper either. Some have entirely different form factors with different types of dies.

Also, if you haven't used a Molex crimper they have a spring-loaded button thing on the back that pushes a plastic piece forward between the open die, which holds the terminals. Check out this video. They are not universal either and each is designed for a narrow range of terminals. Molex makes dozens of different crimpers. You can fit other terminals in there sometimes but they won't hold well and will be too wobbly or too big. Some of the terminals require unique finished crimp geometries to fit in the connector housing, and so crimpers for them won't work well for "general purpose" terminals.

I recommend staying away from the OEM crimpers - as nice as they are - until you have a specific need for one or you need to assemble a ton of connectors. If you're putting connectors in something mission-critical or very hard to get to, it may be worth it to get the correct OEM crimper to ensure crimp quality. For most hobbyist purposes though - not worth it IMHO.

Instead, I'd suggest picking up one of these. So far I like it a lot more than the "engineer" crimper which I've also used extensively. The IWISS is actually a "combo" of 2 of their other crimpers and covers a pretty wide range of terminals. It will also crimp both wire and insulation in one step, and the die is sized differently for those portions. Much more convenient, twice as fast to do a terminal. The Engineer crimper requires you to first crimp the wire, then the insulation (or vice versa).

The engineer is OK but it's not nearly as good for small terminals. The clearances inside the closed die are quite large, terminals get jammed in there and misshapen or broken. Or the part sticking out of the die is bent by the crimping process. It's also not correctly toleranced for insulation crimping so you have to do it by feel or you'll just crimp through the insulation altogether. I've pretty much decommissioned that one. The IWISS has so far been very good, just squeeze all the way and done with good insulation crimping.

Of course, if you know you will only use that series of connectors and you don't mind the outlay for OEM crimpers, then by all means go for it. They are super nice to use so if you can justify it then more power to you!

I was going to post this, including an Amazon link, possibly to that same product page. While I await your wisdom, future self who is somehow British, let me add that a decent crimper is worth its weight in gold for this. Pliers will work, but it's a nightmare to do once, much less five times for a 4S balance plug. These look good, I'd link mine but I bought a set meant for larger terminals, and while they work on the small stuff we use, they're not supposed to.

For OP's benefit, (paging /u/Brookshire) the best way I've found to do this is to strip about 1~2mm off the wire, put the terminal in the crimper and close it until the ratchet engages and the jaws are barely holding it, feed the wire into the terminal, and then finish the crimp. The little tabs should be on bare wire, the fingers should be on insulation, and no part of the wire should be past the boxy bit at the end, it screws with the pins fitting when you plug it in. You can add a dab of solder before you put the terminal into the plug if you want, but you shouldn't need to and it might not fit if you use too much solder. The terminal is supposed to go into the plug a certain way, but honestly it's easier to look at a finished balance plug than to have me fail to explain it. ¯\_(ツ)_/¯

another LPT: engineer crimpers are a thousand times better than the ratcheting style. But double the price, and yes you need two to cover every style of crimp out there.

https://www.amazon.com/Engineer-PA-09-Micro-Connector-Crimpers/dp/B002AVVO7K/
https://www.amazon.com/Engineer-PA-20-Universal-Terminal-Crimping/dp/B002AVVO7U/

vs cheaper ratcheting
https://www.amazon.com/dp/B01N4L8QMW/

I did my last PC with this: https://www.amazon.com/gp/product/B01N4L8QMW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

you can pull pins with two staples plenty easy. Its really pretty easy. Just triple check your pinout with a multimeter on the donor and replacement cables.