This is an essential, but technical, pain. Do it, do it promptly, and do it well. To make life easier on yourself, get the book Copyediting, A Practical Guide, by Karen Judd (ISBN 156052143-0). Read it, keep it by your side while you go through your manuscript, do the best you can. And be grateful that a real copyeditor will be doing the same thing. My eyes don’t pick out a third of the things that a professional’s do, but I do manage to find and correct some things that might otherwise get missed.