Whats the best way of topdressing a lawn, and whats best to use for topdressing
For the last few years we have used the Symbio products - not the cheapest but well worth it. Lots of compliments on our lawns, and they withstand plenty of traffic during NGS open days. Here is the link
If the lawns not too big you could mix your own using good top soil and course washed sand, mix according to your soil conditions, more sand if drainage is poor, more soil if it's on sandy soil.
Greg04 would mixing compost in help too after useing a hollow tine airator