Perhaps good enough for roadwork, but . . .
For competition, I do the following:
Lap the valves, diluting the paste with light oil after every twenty or so rotations.
Wipe the surfaces with facial tissue until they're clean.
Drop the valves in and fill the chambers with rubbing alcohol. Do NOT fit the springs or oil the faces.
Wait a few minutes.
Check the ports for wetness.
Repeat the process if leakage shows.
If you can't get a good seal this way, you might have a bent valve stem or an off-center valve guide. Stop and fix the problem.
Remember, the purpose of the valve spring is to follow the cam at all engine speeds: it's not there to seal the valves. That's your job.