I have a 'knotty alder' front door that was refinished by a contractor last August. However, because the lower panel of the door has already deteriorated due to sun exposure, I decided to sand the existing spar/urethane for a smooth finish before applying 2 fresh coats. However, after smoothing with a sanding block using 220 grit, there are several streaks where more of the urethane was sanded down due to unevenness of existing application (see photo). I'm hoping that fresh coats of urethane will blend in and eliminate these streaks. I plan to use a 320 grit sponge between the two coats. Just hoping that my initial use of the 220 grit had not created a major problem!
Finally, I believe that I should wipe the sanded areas with mineral spirits before applying each coat of urethane. How long should I wait before applying 2nd coat of urethane?