See YouTube description for full details and links.

Key bits of speed tech are:

• 1440 Requisition and 360 power are the minimum resources needed for 4 rockets launchers across all 6 marine squads. This assumes you immediately get the HQ upgrade, the Heavy weapons and target finders before anything else. The target finder don't make much difference but you can fit them in without too much trauma so I added them. This also assumes you don't take any losses, which I did in this run so having a bit of extra resources in the bank would be useful in most cases.
• Once you hit 360 power you can destroy the 2 power generators. The Chapel Barracks can be destroyed immediately after starting the HQ upgrade research. Both give a small additional requisition boost.
• I use the autosave rather than creating my own save point because its quicker. The autosave will fire - I can't stop that from happening, so rather than experiencing the pause of a save twice, I use the autosave and accept the possible problems that create like keeping the Dreadnought alive and risking not having good Tactical squad placement. This above all other things makes the method shown risky and not suitable for runs of the whole game.
• There is some notable RNG here - the spawning horror locations are random and while they can be mostly ignored, they will kill a few tactical marines which will lower damage on Sindri. Also the Eldar and pursuing Chaos forces need to run back to the Eldar base, sometimes Chaos wipe the Eldar out and then just stand there in the way. Its very annoying!
• Sindri doesn't always just stand there, sometimes he barges his way through the marines to go back to his base after loading the autosave. Other times he actually just carries on fighting until a gap is made and then runs back to his base after loading the autosave.