Soil prep for additives and slope/drainage for new sod
I'm preparing my yard to lay down some new sod. The area is bare soil, but not hardpack. My area has a fair amount of clay/sand mixture (southern california). I'm will till the soil next weekend and have two questions before I till. My first question is about soil additives. Like I said, the soil doesn't seem too bad now and I've been told that gypsum is a good thing to add. Should I add anything else while I'm at it?
My second question is slope prep. I have a surface-level drainage pipe (existing from previous owner or builder) and want to be sure I have good slope that feeds drainage to it. I don't have a transit and tripod and want to know if anyone knows of a good alternative way to measure the slope. I was thinking about mounting binoculars to my "fixed" fence and using a 2 x 4 with a measuring tape mounted to it. But I can forsee that the mounted bonoculars won't be very accurate once I start moving them from side to side. Any inexpensive ideas would be appreciated. Thanks.