The isopon filler is, as @Pond said, very 'claggy' so doesn't spread easily. But that's because it has more, much more, glass fibre in it.
It's not meant for fine spreading. It's meant for bridging big gaps or moulding new parts, joining panels.
The easier spreading stuff is for filling smaller holes/gaps and generally 'spreading' thinner.
So use both but for different jobs or different stages.
It's not meant for fine spreading. It's meant for bridging big gaps or moulding new parts, joining panels.
The easier spreading stuff is for filling smaller holes/gaps and generally 'spreading' thinner.
So use both but for different jobs or different stages.