To do a fishbrain you should use the same steps as a Rocket Makio but it should be topside and a fishbrain is one of the hardest Topside tricks there is. Before you learn a Fishbrain you must learn how to Topside. If you want to do a true fishbrain you must get crouched down low so that the frame of the skate it on the top of the utensil. You should approuch the utensil at a moderate speed with your topside foot behind your grabbed foot. If you are going to do a "Rocket Fishbrain", Fishbone then just kick up your topside foot and your momentum should get you down far enough to grab your foot straight out. If you just want to do a Fishbrain (Topside Makio) then do the same process but you don't have to crouch low.