Thread: Exterior 2-part filler with long working time?

I need to fill a lot of cracks, some wide, some tiny, in about
100 blackbutt ballusters for exterior use. They'll eventually
be painted, so I don't need to make the filler look pretty.
It just needs to be paintable and stable in full exterior exposure.
There's also some shallow depressions in the timber, and I've
that ordinary 1-part fillers don't adhere to the surface well
enough for this.

In the past, I've got best results by pre-painting with oil-based
undercoat (2 coats, with several days drying time between each).
Then I'd use the standard "builder's bog" 2-part filler, allow it
cure thoroughly, then sand and do 2 more oil-based undercoats,
before 2-3 topcoats of acryllic weathershield.

This is fine -- except that standard "builder's bog" 2-part filler
can be a pest when you're working on a large amount of fiddly
imperfections -- because it sets too fast. I always end up wasting
a lot of epoxy. And re-mixing tiny quantities a hundreds of times
is a pain in itself.

So I'm wondering about other solutions, such as epoxy resins
with filler added. Eg., West Systems, or International's "HT9000"
series of products.

I have some questions to which I couldn't find answers on their
websites. Can anyone here help?

1) Are these products ok for filling timber or are they likely to
come loose as the timber expands and shrinks? (Someone
once warned me that ordinary fibre glass resins can lift off
timber over time.)

2) Will these products accept an oil-based undercoat on top?
If not, what intermediate coat could I use so that I can put
acryllic weathershield as the top coat successfully and durably?

TIA for any advice/experience/suggestions.

Cheers.