I have an old garage building with a flat roof made of concrete. It
leaks a little bit. On part of it there is an asphalt coating and on
some parts you can see the bare concrete. It is structurally sound.

I've talked at times to several roofers to see what should be done.

One roofer suggested a rubber roofing but that is a pretty big deal and
expensive and I'd think overkill.

The simplest and cheapest solution is just a coating of some sort which
is what I'd like to do. What kind of experience/experience to people
have with this? And are there some recommendations on types of coating.