The usual way to do it is to slice the sod out, put dirt in the hole to level it and put the sod back in.

I have had success with this technique.

First carefully cut the sod from the low area. Make sure you take the sod just beyond the edge of the depression.

Next add fill and compact the depression until it is level with the ground. (Once when I did it, I drove the tractor with a lawn trailer round and through the hole with my 60 year old wife in the lawn trailer, both or us laughing like crazies. I don't know what the neighbors said.)

Which ever method you use to compact the fill, carefully re-lay the sod on the hole. Water until the grass is reestablished.

With 4 sqft, you should be able to do it in a morning and when you are through no one will ever know there was a depression.

To answer your question, yes, you can sprinkle sand or topsoil over top of the grass incrementally. Once a week should fix it in a few weeks. Just don't bury the grass blades or you will kill them.