So, I am trying to brush the sideskirt but I just can't seem to get it looking realistic like the rest of the car. Any tips would be great.

what's wrong with it ? i don't see some problems

Looks a bit better now.

The right part of the sideskirt looks a bit toony, try using some of the reflections just above it and see if it looks better. Also i think you might be using a bit too much smudge or blur.

-use the paint color and brush
-or overlay parts on the skirt (c&P) , play with opacity and blending modes..
-or select parts of the skirt and play with the clone tool , using stuff of the ori paint...

the side of the skirt where it go's into the well needs shading ...
and the whole skirt lacks shading and highlighting ... bottom part of the skirt needs shade (darker colors)
also anmd this is hard to explain , some parts just need shade , lets say under the door there is a highlighted stripe on top of the skirt , you can see that below the highlight its already a tad darker that needs more shade

you have too look at it like , how would light hit it and what shapes are in the skirt , i have "studied" real l;ife cars and also all objects around us to see what lighting and darkness does
all objects have this , and the shape and direction of light dictates how the highlights and darker colors are

a lot of words but in general the fact is in chopping hightlights and shading are more important as reflections
reflections dont give depth