Another useful technique to have up your sleeve is the "hall of mirrors".
It's described part way down this page
https://www.davidcortner.com/slowblog/20110815c.php
Essentially if you look down the tube at the right angle you can see an infinite set of reflections. Line them up behind a spider vane and you'll see them curving off to one side or the other if the primary and secondary mirrors aren't aligned.
I found it useful to iterate this technique to adjust the secondary with use of a laser for adjusting the primary (esp. the Glatter with the holographic circles attachment).
This gets it close enough that a minor tweak with a star test should be all that's needed.