a compost/soil blend would be a waste of your money, time, and energy because you already have all the soil your lawn would need. Most likely that lawn does need organic matter. Depending on the type of spreader it may be used to spread that compost, as long as it is not too lumpy.

The basic idea is to spread about that 1/2 inch, but being careful to not cover the green grass leaves so they cannot get the sunlight they need to convert the nutrients they pull from the soil into what the grass needs to grow.

actually I do need some extra soil as the grass was planted in very poor soil ( looks like mostly clay).

Yes, you can use an appropriately calibrated drop spreader. But I find it way easier to just do it by hand - just a large soil scoop or shovel that I toss out from my wheelbarrow, repeating the process until I have achieved the approximate depth I want. Or just dump it by shovel loads in a pattern across the lawn (or in specific areas if that's what you want) and rake to even and level.

The take-away from this is that you do not need to be overly precise :-)) The lawn will quite easily grow through an inch or more of soil, soil/compost, just compost or sand.

What passes for soil here is Lake Michigan beach sand and that does not hold either moisture or nutrients well at all unless copious quantities of organic matter is added. Adding just organic matter to the soil you have will eventually make it better. There is nothing wrong with clay as soil except the lack of adequate mounts of organic matter. Adding sand to clay will do little unless you add very large amounts, enough to change the ratio of sand to clay to about 50/50 and that could raise the level of your yard quite a bit.

I'm going to use the wheelbarrow method of spreading the compost soil. looks like the easier method. thanks