a decent syringe of heatsink paste is $7 on newegg or amazon
there's a reason you won't seen thermal pads as the interface between a cpu's heat spreader and the underside of a skived copper heatsink in a high wattage per socket, dual CPU 1U or 2U server, where the heatsink has to be really efficient.. it'll be a factory applied paste.
So in that instance, if the thermal pads are reasonably well installed, the components should be just fine, since we're working with much looser tolerances.
When you need active cooling, the manufacturing complexity increases to the point where the convenience doesn't really make sense, since you have to get it right, so thermal paste is the way to go.
I do not ever re-use pads. I have a used pad on my desk at work that shows an indent of the chip that was pressed into its other side... and you can read the part number and lot code laser marked into the chip. If the pad conforms to that but then can't relax back... it's never going to make good contact again. Full stop. (Granted, this was an extremely expensive thick gap-filler pad [TG-A9000, I think] for a particular application, and performance will vary.)
if the tolerances are tight enough, if the heatsink doesn't even touch the VRM thermal paste won't do nothing.