How do i do this spray paint brush effect on an image exactly like this Amiri Tee?

[LilVill5D19]

[Trevor.Dennis]

If you are after an airbrush effect, then select the brush and set Flow to a low value (I used 10% below).

You can either click on the airbrush icon in the Options Bar, (my green highlight) or check Build Up in brush settings (my cyan highlight).  It's exactly the same.

If you move the brush opr stylus at a constant speed, then it will paint a low opacity line.  If you pause the brush though, it will continue thickening the line, just like a real airbrush.

However, that's not how I would create the illustration you used as an example.

I would make a circle with the Eliptical Marquee tool and use Edit > Stroke on a new layer.

I would make that layer a Smart Object, so you can continue to fine tune any effects you apply to it.

You can then use Gaussian Blur to soften the line.  I used a value of 10 pixels below

This approach allows us to be more accurate, and we can fine tune our linework.

You can also create a path and stroke it. People like Bert Monroy use this trick to get super accurate line work.

If you use a Pressure Affects Size brush preset, and check Simulate Pressure when stroking the path, it will create a tapered line like below