You can use what we used to call a drag or a go-devil. Have you ever seen a stone boat? You can also chain some logs together to break up the clods, sort of in a harrow configuration with the logs a foot or so apart. They need to be at least 8", 12" is better, and fairly straight. You don't pull them long ways, you pull them cross ways.
It shouldn't be hard to find a cheap harrow. Just about every farm has a couple in the weeds. Maybe you could borrow a disc. I use an old John Deere pull type cover-crop disc because it does a better job of cultivating than any 3-point disc I have ever used.
See if you can find directions for that plow. It used to have a trip rope that raised the shares when it was time to turn a corner. After the turn, another pull on the rope dropped the shares back into the ground. It also had coulters that cut the sod in front of the shares that may be missing. It will still work without the coulters, but not as efficiently or cleanly.
If you haven't plowed before, you open up a couple parallel lands by plowing long ways through the field and back, casting the dirt to cover in the center. Leave more than 1/2 of the width of the field between the lands. Plow out each land until you reach the fence line, and leave a dead furrow along the fence line. Then plow out the space between the two lands (remember, MORE than half the width of the field between them), leaving a dead furrow in the center of the field. Then plow out the headlands where you turned around for each furrow. If you have drainage problems, a dead furrow will make a serviceable ditch to drain winter wet spots. The next year you start with one wheel in the dead furrow and reverse your lands and furrows to put the dirt back where you got it.
A disc won't move dirt sideways like a plow will. You can do contour farming with a plow and it will hold up as you work up your seed bed.
