Crates and holes in your asphalt surfaces are annoying to the say the least. They can make your asphalt look old and worn down. Craters usually form due to an issue with the soil below the asphalt. If the crater turns into a full fledged hole (the bottom basically falls out and crumbles), you will have a bigger problem to fix. Also, just adding sealcoat to your asphalt craters isn't going to make them any smaller. In reality, you need to patch the crater to fill it in before you add the sealcoat. It isn't that difficult to do if you use the right products.
Asphalt patching is different from sealcoat, but it is very easy to use. It comes in large premixed tubs, so it is easy to apply. It is important to use cold formula asphalt patch in all of your craters to make them level with the concrete surface before you apply any sealcoat. Patch dries much harder (closer to what asphalt feels like). The sealcoat is only meant for thin application. If you fill in a large crater, it will dry rubbery and soft. So, patch the hole to fill it in with harder material. Using putty knives is the best way to apply the patch. Try to scrape the top and mold it to create a smooth and flat top surface. However, it does not need to be perfect because the sealcoat will create a smoother surface.
Applying the Sealcoat
Sealcoat is more like a liquid or gel. It is runny. When it dries, it only levels out to a few fractions of an inch. So, it is not going to permanently cover cracks, unless they are tiny. So, it is important to patch all of your small cracks, and not just your large holes or craters, before you apply the sealcoat. The sealcoat is mostly self leveling, but you need to spread it around using a squeegee broom. This is a two person job, if you don't have a sealcoating machine that professionals use. If you just have a bucket of sealcoat that you are pouring onto the concrete and then spreading around, you need a helper to pour as you use the broom.
A newly patched and sealcoated piece of asphalt is going to look cleaner and more polished. It is a messy project, but the labor is not that hard if you have the right tools.