I filled in areas where I had inadvertently sanded through the epoxy on my Skerry. This was more of a problem in some areas than others. (E.g. none on the the bottom, more on the sides and on the top of the gunwales. This for now is all on the inside. ) Anyway, I needed to resume sanding. What grit should I start at? Then what? I don’t want to make the same mistake as before. Should i do it by hand rather than with the orbital sander? (I’m doing the inside of the Skerry.)
Are you planning to prime and paint or varnish this area. Either way the Preppin Weapon sanding block is probably the way to go. The RO gets you into trouble a lot quicker.
For painted areas I filled the weave with micro balloons. Sanded 150, touched up burn through, sanded 180, faired a little more, sanded 180 wet, then primed, then faired a little more and started stepping down to 220. Spot primed, scuffed with gray scotch brite. Primed again. Then scuffed with gray scotch brite, then paint, then gray scotch brite then paint. I think a gray scotch brite pad is roughly the equivalent to 500 grit. My result looks a little imperfect but I’m happy with it. If you are seeking like an new car standard be prepared to do twice this level of effort. In most cases I rinsed off dust between primer/paint coats with either denatured alcohol or just hose water. Some high build primers hate water so beware.
Thanks. I’m varnishing the inside and, as I say, am going back after applying a very thin coat of epoxy over the areas that I had sanded through with my orbital sander. As you suggest, I’m leaning toward just hand sanding. But I wasn’t sure at what grit to start. The new coat of epoxy still has all the pitfalls of the old–some very tiny pitting that needs to be sanded out, I guess. But I don’t want to sand too much!
When in doubt start with a high number grit for a pass or two, evaluate. Is it doing anything visible? Is it just filling with dust before it does something visible? Is it doing too much too fast? Adjust accordingly. Also don’t be afraid to wet sand, it’s surprisingly effective. Also some parts need more than others. An epoxy run or something might have you stepping into coarser grade paper. I had a couple of blobs on my deck that required a dadgum die grinder. All I can say for sure, is you will know a lot more about sandpaper when your boat is finished than you do today.