How much side to side play, as in valve guide wear?
Pull valve down about 1/4", and see if it moves sideways, one hand on the valve stem, one hand on the valve head.
If it moves more than a couple thousands, probably valve guide time, exaust vavles are more prone to guide wear.
I use solvent to test valve seats, just pour into intake/exhaust ports, if it runs out valve seat, not good.
Oh, use paint thinner, a lot cheaper than solvent, that's what I use now, same thing, darn enviromentalists.
If you have a dribble in about 30 secounds, should ok.
When grinding soduim valves, do not use water based coolent in the valve grinder, they can explode, use atf fluid and be gentle.
True the grinding stone often.
Lapping valves in will take a long time to wear much metal off, unless your're doing it with a drill motor, which I have seen some people do, lubricate the valve stem if you use this method, but I don't recommend the drill motor method.