Following yet another coolant hose failure (due to fan damage) I will be replacing all the coolant.

I like the look of the vacuum pumps to refill, but has anyone used one?

I understand the way it works, but I don't want to "over vacuum" and break seals etc, so may need to vacuum twice. How does that work? My simple mind says that if I vacuum with some coolant in the system, it will just suck that out rather than create a vacuum?

Or I am being thick, again?

I use one most weeks - never had a problem although too deep a vacuum can apparently cause water pump shaft seals to invert.
Vacuum is vacuum, regardless of the space you're evacuating with it, we use it on fully & partially drained systems, it's rare to draw any coolant out, when it does come out, it's only a mist.

Vacuum to the red line on the gauge, it'll be fine - the benefit is that you don't have to go through a convoluted bleed process (unless it's mostly filled and there is no clear path to vacuum the higher parts of the system), it's also a good reason to drop as much coolant out as you can and refill with fresh. Modern organic coolants do have a finite life.

Perfect, thank you.

I have just ordered one