Hi,Dian.I actually like the finish that I get with a brush,even going to try a scrub brush for a more defined look.However,in my limited experience of getting rid of them,you could sand down the surface with some coarse sandpaper or try brushing on more of your mix,across the grain of the set concrete,then wipe off excess with a sponge or cloth.The sanding has worked for me,but I can tell ya that it's a load of work to do by hand.I've got a 3 head orbital sander made by Ryobi that I've had good success with,but the concrete dust that results destroys the bearings(guess it wasn't made for this kind of use!),so I bought a spare sander when the local supplier(Canadian Tire)told me that they were discontinuing the product.Because the heads tilt,the sander is great for rounded surfaces,like the spheres I work on(and,am slave to!)
Anyhow,good luck with the chair.
Cheers from here
Rick