We can always depend on industrial designer Eric Strebel to put a ton of effort into every project he makes—especially when it comes to his YouTube videos that unveil many design tips and tricks.
In his latest, Strebel showcases how he makes his prototypes look so dang remarkable—from filling imperfections to achieving that perfect coat of paint.

Starting with a cellphone holder mold he made for a previous video, Strebel coats the mold in automotive primer to seal imperfections.
Once the primer has dried, he marks the still-unsightly holes and inconsistencies with a pencil before covering them in another thin layer of spot putty.
With the holes filled up, he sands down the entire body using a variety of sanding blocks. Since this particular mold has an irregular shape, Strebel uses different blocks to get into those weirdly shaped crevices. This process of primer spraying, putty filling, and sanding continues until the mold is smooth and free of imperfections.
Strebel makes a mistake by chipping off a bit of Bondo from the mold. To fix this, he removes the primer from the chipped area, takes a bit of glazing putty, and makes a new corner before continuing to sand down the prototype.
To help with the final stage of sanding in the concave area, Strebel creates a makeshift sander by laying down some Bondo onto and connects it to a piece of PVC pipe.
He then takes the Bondo-infused pipe and lays down some strips of sandpaper to make a crude sander explicitly designed for sanding this portion of the mold.
After a couple more sprays of primer, he moves onto a more heavy duty 400-grit sandpaper to get that final smooth finish. As the mold gets smoother and smoother, he adds a final coat of white primer and sands it with 600-grit sandpaper before going through the painting process.
After spending hours priming and sanding, Strebel seems relieved to be doing something different. He lightly sprays the white mold with a raspberry coat of paint, working from the bottom upwards.
You may have noticed a small hole at the bottom of the mold. This serves as a way for Strebel to pop in a small peg and flip the mold for painting on the other side. Once it’s flipped, he continues with a light coat of paint before coming back and spraying the entire mold once more.
As with all his design works, you can find more of Eric Strebel’s sagely design advice on his YouTube channel.