| How will epoxy bond to glass fibres with vaseline on them?
| Wax is harder (when dry).than vaseline, so shouldn't stick to the fibres, imo

We had the same concern. We took a piece of glass and put a small amount of Vaseline on it and heated with a gun and spread it out with a brown paper napkin. The heat makes it spread like mad. The reason for the brown is that it changes color to a darker brown when it gets greasy. When the Vaseline was well spread, we then took another clean napkin and wiped the area down while heating. This absorbed any extra Vaseline, leaving a very, very thin film.

When cooled we laid a new unfolded brown napkin on the surface and put a weight on it and dragged it around, we saw no Vaseline on the napkin. Unfolded brown is very thin and changes color.

So we thought we would not need to worry about the fiberglass.

Of course, with II, the fibers never touches the mold anyway.

In my case I have only done this once. And I will be doing it mostly weekly. I'll give updates.