Jump starting from a power pack

Wanted to start a thread for specific instructions and the use case I just had (all this information is from multiple threads on here, so hopefully someone else will use the same search terms as me and find this information useful).

I have a sticky boot lid, which meant I didn't realise I left the internal lights on for 2 days and had a completely flat battery. Used the mechanical key to get in, popped the bonnet then located the fuse box and found the special prius "+" red jump point.

I have one of these mini portable power jump starters (this one

but many others available!).

The problem I had, this kit came with very short leads, so I had to use the screw on the bulk head (looked like end of suspension mounting) behind the fuse box for the ground. This worked okay.

Hit the "boost" button on the power pack, car alarm went off (quickly disabled with the key fob) however all I managed to do was power the battery enough to turn radio and lights, etc. on. which just drained the battery charge. Quickly realised my mistake, boosted again (waiting 1 min between as it says in the power pack instructions), turned everything off this time, but not enough charge to "Boot" the main battery. Boosted again, tried to power on but it went flat. So this time, I "boosted" once, didn't attempt to power on, boosted again (1 min later), and this time it had enough charge to boot the main battery, job done - ready light all okay, ICE running, internal battery nice and charged up 20mins later.

I will be replacing the 12v battery at the next service (Oct) as the car is 2nd hand and I don't know the condition of that battery - it went flat 6 months before when one of my kids left the internal light on (didn't spot it), so I think the 12v battery will be in a bad state.