is very much like a pair of snap ring pliers- two points that go in the button holes.
It just has to hold the button steady while you unscrew/screw it. Don’t overdo it since it is just a little 2mm grub screw, I have one that got rounded trying to get it out.
The preload bolt is reassuring but by all means not compulsory.
What is really important is to have an Allen (aka BTR) bit which is a perfect fit to the crank bolt. The crank bolts have a tendency to round up if you have a wrench which is marginally too small or with too much play. And if you search the forum, you’ll see plenty of horror heart breaking stories of stuck bolts…
Thanks both. Useful info to know and have in mind. Super excited to get to try and learn Schlumpf riding, but also aware of some of the pitfalls if not prepared tool wise when using / maintaining the system. Especially on a M02xx series given the age. Happily it looks like it’s never been used and stored in a bedroom!
All being well it’ll get rebuilt with a BrakeFast set up too