We have answers.
The liquid version has no fibres it can be applied in a single coat on less porous and smoother substrates and two coats for more porous and rougher surfaces unlike the brush version two coats can be applied quickly around 10 minutes between coats.
With the fibre reinforced version applying a second cost before the first is dry could lead to damage caused by the brush creating gaps or breaks in the original seal.
We would prefer you use a professional applicator, however the actual spraying technique is quick to learn and the equipment relatively easy to hire, if you understand the principles of airtightness and can handle a sprayer then you will probably do a good job.
No there is a white version
Using the sprayer around 300 linear metres a day.
Pretty much anything from paint to plaster, render or dry lining.