Lawn Dressing Post Aeration

Since the original turf was laid about 3 years back, I have been through a few seasons of fertilising, overseeding and dressing with topsoil. This certainly improves things, but each autumn/winter the lawn still experiences a significant amount of winter die back. The soil is clay based and so I think drainage is a good part of the issue (although it doesn’t suffer from pools of standing water, it does not drain especially well).

My current plan is to core aerate, dress with either sand or grit, and then overseed and dress with topsoil. 

My query is around ratios and quantities. What do people think would be the best:

     - Horticultural grit vs sharp sand, or a blend?

     - Rough weights per square metre? (I’ve seen little guidance on this in other forums)

I don’t want to smother the existing grass, but want to apply sufficient that it at least does something.

Thanks in advance for any advice.