I'd be leery of hammering on the night sights with a hammer and punch. I'm not saying it cant be done, as rc, and I'm sure others, have obviously done it, but if you get a little heavy handed, you could break the vials and your $80 set of night sights are now for scheiße.
I have yet to encounter sights that were loose or easily removed without a fair amount of pressure. Same goes for the ones replacing them.
All of the new Mepros I've put on have been slightly oversized. I run the base of mine across a piece of emery thats flat on the workbench and just barely remove the finish on the base of the sight. That seems to do the trick and the sights are still a firm force fit. If you get carried away and remove to much.... back to for scheiße. DONT file of sand on the edges! Only the base.
One other advantage to the tool, it has witness marks on it that get the sights centered on the slide. I've done about ten guns now with mine, and so far, only had to use it a second time to adjust the rear sight for windage because the sights were not shooting to point of aim.
The hammer method may, and probably will, require additional hammering.