My cousin is getting married and wants me to recreate this cake. I use swiss meringue buttercream for all of my frostings. Trying to figure out the best way to accomplish that. Any ideas?

Maybe dragging a spoon over the icing?  Or just using the rounded tip of an off-set spatula?

That's an easy one.  Ice your cakes and smooth down a bit, doesn't have to be completely smooth, just relatively flattened.

Place the cake on a turn table and press the tip of your spatula against the cake with one hand and, with the other hand, turn the turntable.  As you make a complete turn, move the spatula's tip up a bit and make another turn.  Keep doing this until your reach the top of the cake,

Alternately, you can get a similar look with strips of fondant that are ruffled on one edge then attached to the cake row by row from top to bottom, but the buttercream technique is easier and faster!

Thank you. :) She absolutely does not want fondant and I was afraid that my SMBC was not firm enough to create the look created in the picture using traditional butter cream.

Oh yes, SMBC should work fine for this technique.

Here's a video showing several rustic techniques...this particular one starts at about 1:45 into the video.