Say I have an assembled PCB with a QFP package on it. This device gets damaged and I need to replace it. Getting the device off is straightforward, but now all the pads have solder blobs on them. Is there a standard way of cleaning these pads off, so the replacement device will sit flat on the pads again?
There are several ways to manually remove solder
For SMD components (and in general too) I find desoldering braid (solderwick) the best option.
You can use solderwick or a suction gun. Solderwick is probably the easiest.
I would use solder wick for surface mounted soldering. I usually add a little more flux to the wick so when you heat it up, a lot more solder gets removed. Also if your doing through-hole vacuum solder removal is the easiest.
Hope this answers your question.
My experiences attempting to desolder stuff with generic own-brand wick were sufficiently bad that I avoided wick for years, I could never seem to get the stuff to suck up the solder. Then I moved to a different research group and started using wick from the likes of multicore and servisol (and admittedly also a better iron) and it was much better.
It is important to fully melt the solder (you should see the wick change colour as the solder is wicked up) and to remove the wick from the board while the solder is still fully molten. Ideally removing iron and wick together. I recommend leaving the wick attached to the roll so it cam be easilly manipulated while hot. If you let the wick cool too much before removing it you can easily rip pads off the board.
Suction tools can be handy for removing bulk solder without wasting a load of wick or resorting to bashing the board on the table but are not so good for getting groups of small pads flat and clean.