Using solder paste instead of soldering wire for through-hole parts
I've done it, and it is far messier than wire solder, with negligible advantages.

Basically, through hole soldering requires a lot more solder then surface mount. Therefore, you wind up building huge mounds of solderpaste on every component hole, which then gets pushed around as the rosin in the paste boils off during soldering.

The end result is solderpaste/solderballs all over your PCB, with little of it where you want, on the component leads.