How long do we wait between filler coats? I've slathered it on heavy in the past and done one coat but this time I've put on a single first coat a bit thinner, (weave slightly shows) and got a good finish. I could let it cure and paint it then but it seems to me an extra coat would be perfect. Right now, any extra filler "balls up" (causes lumps) in the first coat. I'm using Blanchard's formula with some alteration, Thompson's Water Seal instead of spar varnish. Any advice?