Does it offer protection?
Not really, it’s purely for visual enhancement and should be covered over with a wax if you want to protect your paintwork; you can use sealants over the top but they may not last as long as usual because the paint surface becomes so slippy (waxes are less fussy).
Will it wash off?
It generally lasts a few washes but is not a long-term solution. Avoid strong detergents, solvents and techniques like claying and polishing. These will remove glazes.
Can it be layered?
A couple of layers are always recommended for coverage; whilst three or four coats may give some extra gloss it does depend on the porosity of the paint and the defects within. Sometimes maximum 'fill' is achieved with a single coat.
Is it safe on all paint types?
Yes, it’s non-abrasive by nature and therefore safe for any paint. Just be careful when using it on old porous solid paints (the faded ones on older red cars for example) as the paint may be degraded inconsistently, leading to patchy application. The finish can't be levelled or buffed out if the paint is too porous. In these cases it needs to be cut back with an abrasive polish or repainted entirely.