To apply puttyfilla for levelling uneven wall, better use trowel or scraper?
After apply, when sanding it, how rough the sand paper to use?

What is the difference between puttyfilla and skim coat?
Which one is better in term of durability, economical, ease of use and final result?

For skim coat, there are powder type and ready mixed type.
The powder type we need to add water ourself.
Use which one better?