It helps having some of the right tools - like fret removal pincers with the end ground away flat so that the blades can lie flat against the fretboard. Obviously something to cut the new fret to roughly the right size, a soft-headed hammer to tap the fret in, then again some flat-bladed pincers or cutters to ship the fret ends close to the neck. Then some files to smooth the ends off, plus the usual fret sanding and polishing materials.