I've done it on a lot of Briggs vertical flat head engines with no problems. Just be sure to clean all the grit out. But you knew that already.
If you use a reciprocating valve grinder, you know to put the spring with the grinder on the valve, don't you? And don't use too much pressure. And take your time.
The reason I ask if you know about the spring is most of those grinders you find at flea-markets have lost all their accessories at some point. And for some reason, you don't find the spring available in most mower parts catalogs. I keep a spring that came out of a automobile wheel cylinder with the one I use at work and it does fine. The spring lets the valve lift a bit without the valve slipping on the grinder while you turn the crank.