When taking on a project like this,
I used other brands such as Herald King, but my preference has always been Microscale. I have to mix scales, using HO locomotive sets and larger freight cars. I've used Microscale S scale sets but haven't seen those in years. A company called Rail Graphics used to make Capacity Data sets and I ordered a whole load of them in O and S scale. Unfortunately those are no longer made. I'm looking to try some O and S scale decals from Tichy.
Never had a problem with decals flaking. My earliest projects are now almost 30 years old and just fine. I've always used spray cans and have experimented to see what brands are safe. After decaling, I flat coat the entire car with several sprays. I used to use Testors DullCote but have found out the hard way, it yellows slightly over time. You notice that more on a item painted white. I've since switched to Krylon for gloss and flat coat sprays.
This topic has been covered quite a bit over the years. There are some here who use some kind of furniture or floor polish... Future, I believe, instead of dull cote.
The hardest thing today is not repainting technique, but rather finding the right decals. Fortunately for me, since I'm doing mostly smaller 027 cars, I've been able to utilize HO scale decals, which are still readily available in the greatest variety of roads.