pull it in with a plain nut then switch it for the nylock :D simples

In theory yes :)

The idea sort of goes down the drain after you have spent hours looking for a UNF plain nut .... Then you find one, just to find out that the ball joint maufacturer has used a Metric fine thread :D

Some manufactures have stuck with imperial threads & others have switched to metric fine.
Strange but True ;)

there is just no helping some people :)

Honestly, I meant nothing by my comments Baz :)

Just thinking from a home workshop point of view, how many folk have access to a selection of metric & imperial fine threaded, plain nuts ?

I have a huge range of old imperial stuff & a fair bit of metric stock too .... So much so that I weighed in, 6 full builders buckets of used fixings during my last trip to the scrappy .... Got hacked off with tipping them out onto the floor looking for a particular fixing, just to find, that's the only one you dont have :o

Yes of course you are right mate, the simplest way to pull a ball joint up, is with a plain nut :)
I guess placing a few flat washers under the nyloc comes a close second.