Creative Solution

Blends come to mind:

Or brushes. In this example an art brush

It's made of a couple parallel lines. Do not expand strokes before creating the brush

Then apply it to a swirl and also apply a wdith profile to that:

When you expand the appearance, you get single paths:

Object Path simplifa will help with the excessive amount of anchor points.

Then apply gradients and again width profiles to those lines:

Various approaches can be taken to create the multi-colored swirls shown in those vehicle wrap images. They can be created entirely in Photoshop or using a combination of the tools within Illustrator and Photoshop. Some people will even sketch out these kinds of elements by hand on paper, scan the images and then hand-trace the results into vector form. The basic vector shapes can then be altered in various ways. If the paths are brought into Photoshop the paths can be used to generate selections that can be modified, such as feathering the selections to soften the edges. Then the selections can be filled, air-brushed, painted into with different colors, etc.

Some of the work flow choices will depend on which application is being used to generate the final vehicle wrap images, be it Photoshop or Illustrator.