I’ve used almost all clear coats out there and TBH it doesn’t really matter that much. Both spray and roll on work fine and each have pro’s/cons. Which ever you use just be sure to put several coats and allow appropriate dry time.
Below is a thread discussing different clear coats and methods for making things grind. Some good suggestions in there.
https://www.slapmagazine.com/index.php?topic=114106.msg3444304#msg3444304Idk what your budget is and this is a luxury, but if you can afford it a cordless angle grinder and a diamond grinding cup. BUT if you don’t already own cordless tools and batteries it gets expensive.
I got about 50-60 ft of a ledge near the house grinded smooth and clear coated in 1 hour & 15 mins. Which is a plus if the spot your fixing is in a high traffic/populated area.
You can forgo the angle grinder and just use a rub brick, just takes longer and is very tiring if you got a lot of ledge to smooth out, especially solo.
For cracks on the ground bondo works great and lasts a long time if done right. I’ve seen a lot of people use bondo to fill gaps and cracks in ledges but TBH if it’s going to get grinded heavily it won’t last long it’s not very hard. Steel stick is great for a spot that has a chunk missing or a small crack and holds up to grinding really well, but is expensive for large chunks/cracks.
Regarding bondo, it makes a huge fucking mess. Wear rubber gloves, old clothes and make sure you have something to mix it up in i buy disposable paint roller trays, something with a lip helps but you can use anything. Duct tape out where your bonding, get some painters sticks to scoop the shit out and mix with and some plastic putty knives to lay/spread it out how you need it.
Regarding concrete, it has nothing to do really with the type and everything to do with your technique. Just google how to get a smooth Finnish on concrete and study up. Your first time is not going to be as good as you want, but keep trying and practicing and you’ll improve. I’m still not as good as some buddies but I’ve gotten decent.