Looking on the web, You Tube it says not to sand the top coat before lacquer.
If you have a spray booth this is probably ok, but if like me you are doing it in a garage then your are almost certainly going to get a bit of dust, bug etc on it.
I did have a couple of tiny marks in the final orange coat so I went over it with 2500 wet and dry and got it glass smooth.
It had gone a bit dull by then and I thought I had screwed it up, so I decided I had nothing to lose. I dried it and then went over it with T-Cut and got the shine right back up.
Then washed with soapy water, rinsed, dried overnight. Next day de-greased with meths and then Lacquered.