Pin holes in filler

[Graham Singleton <100421.2123@compuserve.com>]

I always mix in colloidal silica, about 1 part to 5 by vol of the microballons.
This makes the mix flow much easier. Then I spread out the whole mix hard and
rough with a wide steel scraper, a lot of the bubbles come out then. Finally lay
on the fishing line and scrape down to thickness.
 You could try a low vacuum but in general the mix is too stiff. High vacuum is
no good, boils off some of the resin constituents. 
Colloidal silica is a revelation.
Graham