Today yet another print came out OK -- but far from perfect. I gave up* trying to fix the print. As it was 'failed' already anyway, this would become my first ever 3D painting attempt. And at least, that turned out to be a success. I've kept it simple and low-effort. You only need sanding paper (any), acrylic paint (black/white/silver), 2 brushes (flat wide and as-small-as-you-own) and one glove.

1. Sanding

With medium sandpaper - because that's the only one you own - sand away most of the imperfections. Alas, this will also sand away any 'shiny silver' look the model has. Only sand where there's imperfections to remove, let's not bother with the rest.

With a wet cloth, remove all the sanding dust. Let the model dry for a while. Little or no patience? Use a hairdryer on low heat from a distance.

2. Primer

Skip. (Remember, no patience. This also why we only sanded once. And where it was really needed.)

3. Base layer

With a coarse, wide brush apply silver porcelain paint over the model. Porcelain paint is more liquid than acrylic paint, and will give a better cover between the layers. If you have only acrylic paint, use silver with a tiny-tiny bit of black, and a small-small amount of water to your paint.

For a silver look, follow the print layers as well as painting vertically. If you want a more rough, stainless steel look, paint with rough horizontal strokes so the areas between the layers are not quite saturated.

4. Sanding and adding another base layer

Skip. No patience and silver paint is expensive. By now I've decided seeing the layers is fine, as I'm going for a steel look.

4. Steel (optional)

Mix undiluted silver with a small amount of black. Cocktail prickers work great for this. Take a coarse wide brush and starting at the bottom of the print, apply tiny amounts of paint following the printing layers. Make sure you spread it lighter as you near the middle of the model. It's fine if you silver coming through! That's exactly the effect we are going for. If you feel your design is becoming too dark, wipe away some of the black with a paper towel. The darker silver in between the layers will remain.

5. Shading

At this point, we switch to a finer brush. Take silver, and add some white. Mix and start painting the areas where the steal would reflect. For silver-look, make sure the print layers are filled. Dilute your paint a little and paint horizontally and vertically. For the steel-look, paint against the layer direction with undiluted paint. Add more white to the silver and repeat where more highlights are needed.

Similar for the shaded areas: silver + a tiny amount of black. Repeat by adding more black, and with that more detail to the shaded areas. For steel, make the shade areas more dark, sharp and imperfect than for silver.

6. Eyes

The most tricky detail in the model. If you own an even smaller brush, now would be the time to use it. Use a lightly diluted pure white. Draw the 'outlines' - where the eye meets the skin - first. Then fill in. For the pupils, do not dilute your black paint, and also start with the outlines. Then fill the eye in. You can add a small highlight on the top left of the eye with the silver+black mix you have remaining. (Our eyes are round and shine.)

7. Varnish

If you have any lying around around you can add it as the finishing touch - transparent shiny to reinforce the silver look, preferably matte for the steel look. I might go treasure-hunting in the garage tomorrow.

And you're done! This should be lot nicer than your original flawed print. If not, let me know in the comments with pictures, and we can learn what works and what doesn't together!

Of course, throughout all this you had the glove on your non-painting hand. Right?

Next time

I will no longer buy expensive 'shiny silver' filament. I'll start with a grey basic filament, and paint the silver on.
I will intentionally make scratches in my model, so I have more dark areas to fill for that unpolished steel look.
I might try adding some brown in the mix to make the result feel more natural.
I have some edible metallic silver powder that's way being being expired. I'll try the effect if I mix that in.

Added to my 3D printing materials wish list

Sanding paper with a fine grit (wet and dry use)
Fine acrylic pen (black and white) to give me more control about the eye-detail
Acrylic putty for fixing details
Epoxy paste to create ear-prosthesis
Finer and much-finer pencils

Eventually

I want to be able to print the Gayer-Anderson cat, and paint it until it looks exactly like my bengal cat Minx. With an Egyptian flavour.

* I've recently printed a lot of cheap glow-in-the-dark filament, which I blame for seriously clogging the nozzle. When my prints started to 'finish' (100%) with many of the top layers missing, I decided it was enough. I switched out the filament, and cleaned out the nozzle. Now it's better, but not perfect yet. (See the cover image.) IL3D's Squeak model is perfect for beginners:

Squeak

30.48MBRelated 3D Model

Just not for my Ender and Me. Although this I might be able to fix by experimenting with the temperature, flow, ... -- are hints always welcome!

How paint can salvage a print