Quit struggling with hastily patched together electronics for your light painting images. Follow [Madox's] example and build a light painting wand designed with your hand in mind.
You wield it much like a sword, but the only damage it does is to the long-exposure camera pointed its way. The RGB LED strip is controlled by the guts of a tiny little wireless router, a TP-Link TL-WR703N. This lets [Madox] connect using an Android device to upload different images. It also lets you tweak the settings like adjusting the timing between columns to match your exposure settings. The custom handle design provides a home and mounting plan for everything involved. It was 3D printed at the Sydney Hackerspace.
This isn’t the first light painting device running Linux. We’ve actually seen the Raspberry Pi used in much the same way but that final project involved using an entire recumbent tricycle to move the colored lights.