OT: Can I Use A Contour Gauge for Shaping Bondo?

[DerbyDad03]

I won't be trying this until the weekend, so I figured I'd ask and maybe get some other suggestions. I also don't have a contour gauge (yet) so I haven't had a chance to test this...

Part of my house is sided with this type of Fiber Cement shingles:

In the past I've repaired some bolt holes by overfilling with Durham's Rock Hard and then shaping the fill with sandpaper to match the surrounding area. Slow, but it works.

I'm going to be painting all of the siding soon and I want to fix a few larger spots that have just been filled and painted over in the past. Holes from a railing and window box that were removed, etc. Since these holes weren't shaped, they are more noticeable.

I was thinking of using a contour gauge to grab the contour of the area above the repair and then drag the gauge over slightly cured Bondo to impart the grooves. I assume it will still take some sanding, but if the gauge can get me started, it might save some time.

Any other suggestions besides a contour gauge?

[DerbyDad03]

I just read a suggestion in the Fine Homebuilding forum about dragging a wide putty knife (wider then the filled spot) across the grain to transfer the pattern.

That suggestion has potential.

[Unquestionably Confused]

Bondo or Durham's and a stiff bristled scrub brush or even a wire brush. Fill the area and play "artist" while it's still relatively wet. Let it dry once you have it looking "right" and then come back after it truly sets up and knock down and high points with sandpaper.

Different material, I know, but I removed a through the wall AC sleeve on a cedar sided (plywood) wall. I slightly enlarged the opening to make it perfectly square and then cut a piece of replacement ply so that it was pretty much a press fit. Coated edges with paintable silicone caulk and carefully, butg quickly "touched it up" with a wire brush.

Hit it up with a coat or two of solid stain to match. You have to be right on top of it and looking for the "repair" to see it. The HVAC tech who came out to charge the lines on the replacement split system I installed had to ask where the thru wall unit had been. I pointed to spot two feet west of where he was looking, he squinted and said, "Oh, nice work!"

[DerbyDad03]

After trying a few different methods, turns out the Durham's and the scrubby side of a Scotch-Brite sponge was the best option.

The Durham's gave me much more working time than the Bondo and the wet scrubby basically reactivated it so I could clean it out from the grooves in the siding. The occasional use of a thin wooden skewer help shaped inside grooves if that where the hole was.

Now I just have to figure out who put all those damn holes in the siding over the past 35 years. ;-)

[Leon]

Woodey and his pals. ;~)