I agree it is probably pin holes. What I have heard some do is to wash out the pinholes with alcohol and use air to blast out the compound residue.

Take some black boot polish and put a few coats on and buff. The black will fill the pinholes and the rest will be removed when polishing.

Yes its a crude way to make things look good but it works.

Fred    

I would say that the compound is filling in minute holes in the surface, that is unless these white spots wipe off with your finger?

I keep coming across the same problem.

In the final stage of flatting and polishing minute white speckles appear in the epoxy. 

My process, 1 st coat , coating epoxy , 8 > 10 hr cure @ 20*

hand 120 dry sand , brush off dust , vacume.

2nd coat , coating epoxy 8 > 10 hrs cure @ 20*

hand sand wet - 320 > 600 > 1200 > 1500 > 2000

everything looks good at this stage even flat finish no blemishes really, just needs buffing up...

so 

machine polish - ( cheap electric car plisher ) onto wet surface -  farecla standard compound G 3 ( SPECKS APPEAR  > farecla ploshiing compound G10 ( SPECKS REMAIN )

it does not always happen but it doeas happen a lot 

any ideas

Ben