I'm not very methodic, so usually I pick tools that at each circunstance might give me a desired outcome. More in the case of a piece like this. I also hardly remember wich specic brushes I used, or where I got them from, but for this case, regarding brushes I think on average it would go like this:







1º- Pick a brush AND an eraser brush with opacity on (if you want also size control) that both have a painterly quality on them (as an example, the last one on the right here has what I mean

2º- Set a big size for them that fits the size you intend for the jet stream. Pick the darkest color the stream will have. With that, painting and erasing, establish the trajectory and the fade out of the stream.



3º- Reducing the size of the brushes and adjusting the light and color, you can progressively add detail on the inside of the stream.







It's also helpfull to use the smudge tool to dissolve unwanted hard edges or details here and there, specially on the outwards of the stream. I use some custom made ones that have a "noisy" result. Or complimenting it also with a soft eraser (on wich you can add a texture).





Then you can use a big soft brush (if you want with textue) on an overlay (or "hard light", or even "vivid light") layer, to brighten things up. In the case of the carrier that effect is more noticeable around the thrusters, where it makes some of a bloom effect.

