Try using wet and dry paper on a flat board. It's gonna be better than an old oil stone, don't ask me how I know that! It's cheaper too.
Getting a good edge is all about maintaining the angle of the bevels. Find something to help you out, I find using a finger works for me. When I hold the knife, I place my finger on the spine of the blade and this sets the angle by making a gap between the stone and the spine. When I push the blade away I use a thumb instead.