Power Sander

Next up we’re going to do some finishing techniques to smooth out the surface and make it shinny and metallic looking. In this project, we used a power sander to help speed up the process. A power sander with detail tip allows you to get into crevices. We recommend starting off with a low grit, like 120 and gradually moving up to a fine grip, like 220.

Sanding details 

The details in between the ears require detailed sanding. Make sure to get in the crevices and smooth out the builds lines. Sand across the entire surface of the helmet, blending the build lines. Be sure to do this in a well ventilated area and wear a breathing mask and proper eye protection.

Filling gaps with XTC-3D

Once we’ve sanded the helmet down, we can apply epoxy resin coating to fill in any gaps. XTC-3D coating from Smooth-On is great for this. It’s a two part solution with a 2:1 ratio mix. We recommend using half of the provided cup. It has a work time of about 10 minutes. We can extend the work time to about 15 minutes by pouring the mix into a aluminum foil tray.

Mixing XTC-3D

We recommend using a foam/sponge brush to apple the resin onto the surface. Mix the two parts in the aluminum tray. It’s a good idea to have a few foam brushes on hand as they’re only good for one time and not reusable.

Apply XTC-3D

We recommend resting the helmet on top of a sturdy bottle, jug or other type of liquid container while applying the resin coating. Wearing nitrilite gloves is a good idea, you don’t want to get any resin on your skin! Avoid applying an excessive amount of XTC-3D. If you apply too much, it’ll start to drip. Apply an even coat across the whole surface. Soak up any excess that may build up near the bottom or crevices.


Rotate the helmet and use lighting to see if there’s any missed areas or uneven brush strokes. Avoid smudging the coating by handling the bottom edges of the helmet. Allow the XTC-3D coating at least hour hours to cure. If the helmet feels tacky after four hours, allow it another hour or so until it’s completely hardened.

More Sanding!

Once the epoxy resin has fully cured, it’ll be very shiny and hard. Now we need to sand the surface again. Let’s use a finer grit sand paper, like 220. Sand down the entire surface. Of course, do this in a well ventilated area, wear a breathing mask and eye protection. Even out the surface until it’s nice and smooth.

Here’s where the time consuming part comes into place. Apply a second coat of XTC-3D coating and sand it yet again. You may want to take a break in between these two coating / sanding sessions. It’s a lot of work!

Primer Filler

OK, Once we've sanded the XTC-3D coating a second time, we can cover the surface with primer filler spray paint. This helps even out the surface and fill in any remaining gaps / build lines. Rest the helmet on a bamboo stack or similar while applying the spray paint. You may need two cans of primer filler to cover the entire helmet.

Apply Primer Filler

Remember to do this in a well ventilated area, wear a proper breathing mask, proper eye wear and gloves  while spray painting. Try not to apply too much spray paint. A light coat will be suffice. Allow the paint to dry for 30 minutes.

Sand Primer Filler

Are you tired of sanding yet? This should be the last session of sanding! After this, it should be pretty darn smooth, like a babies bottom! This time, let’s use a fine grip of sand paper, like 220. Smooth out the entire helmet. Sanding down the primer filler spray paint will make a lot of dust, so be sure to sand in a well ventilated area, wear that breathing mask, eye protection, gloves, all that jazz.

Chrome spray paint

Finally, we can apply chrome spray paint to finish off the surface. Again, place the helmet onto a bamboo stake or similar and now apply a coat of metallic chrome spray paint. Start with a light coat and allow it to dry for an hour. Then apply a second coat to finish it off.


OK now its time to let the spray paint to dry for at least a day. Let the fumes dissipate in a well ventilated area. In the next page we’ll assemble the electrics and mount them to the helmet.

This guide was first published on Dec 29, 2015. It was last updated on May 03, 2024.

This page (Finishing) was last updated on Dec 21, 2015.

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