Not a grading feature, but the bucket will hava a float position if you push the up down foot pedal fully forward it should stick in the float position.
As for getting it level, or sloped one way, it is a persistance thing. I like to take my tiller it to break it into fine material. Then rough it out with the bucket until its close.
Then a Harley aka power rake attachment is worth its weight in gold to finish the top. (beg borrow, rent or hire one) It will do what a crew of 20 with handrakes can and then a little more.
The tires in front of the attachment lengthen your wheelbase to help get the waves out. The rake part separates any stones, debris or clumps, grinds off the high spots and carryies loose fines and drops them in the low points. Criss cross it 2 or 3 times and its ready for seed.
Ken
Clay is tough to grade.
If the clay has any significant amount of moisture it sticks to itself and is difficult to control the cut. Since it is not granular, it does not "flow".
If it is dry, it can get quite hard. If you over work it, the clay will fluff, fill with air and you won't be able to control it.
Your best bet is to try and work it when it has a little moisture and will not quite hold together when you squeeze it in your hand. Also keep your bucket about half full when making a cut or back dragging. The extra weight on the cutting edge will make it easier to control. Make slight changes to the bucket angle as you make any cuts and ease it deeper or shallower as you continue through the cut. A sharp cutting edge on the bucket will also help. If your cutting edge is dull it will tend to ski on the clay and not penetrate.
You may want to pull some string lines and drive some grade stakes. Having a stake will help you keep track of how much you need to cut or fill will help you get to the grade you want.
I would rethink adding sand to a high clay soil. When dry, a high clay with sand mix can get extremely hard. The old saying still applies: "Add clay to sand, money in hand. Add sand to clay, throw money away." The best thing to add to clay is a lot of organic material and till it in. You can add a lot of sand and not make clay soil any better.