I've recently been able to max both crafting and weapon maintenance. I must say that I really like both these skills, as the benefits are quite clear. Since the weapon maintenance skill is new since this patch, I will explain what the ELITE level will do. So every time you repair your gun, you will not have the red bar anymore. So from that point there is no use using any other repair option than Prapor, since he's the cheapest. There's of course different type of people, but I honestly hate using guns that are damaged, so this is ideal to min-max your misfiring chances.
The way I've leveled Weapon Maintenance is by repairing guns before selling them. Since I do scav quite a bit, I got it leveled in no time. A 59/60 weapon gives the same experience as a 0/60 weapon that you repair. And no, you cannot cheese it by doing partial repairs since experience is given whenever the gun is fully repaired.
And for the crafting skill. You can see that it is not synced with Hideout Management. This is not that big of a deal since the ELITE crafting skill allows for 2 simultaneous crafts at the same crafting station, which speeds up leveling Hideout Management. Hideout Management also doesn't need the alternate crafting of products to keep increasing, so from now on I can fully focus on things that maximize my profit rather than finding something between profit and crafting points.
If you have any questions, let me know! Just wanted to share my (perhaps outdated) findings.