Here's what I've found to be fairly practical in a tournament environment, against skilled opponents that aren't just gonna stand there and take it.
Out of Neutral:
You have a few options here. If you catch your opponent in a situation where they have to shield, and they aren't playing a character with a very fast, high range up b (like Marth etc), then if you land behind them with a falling up air, hitting with the back part of the move, you can combo this into many different moves, including back air which will kill. By landing behind them with this move, you are safe from anything but non-grab OOS options. So as long as their upsmash or up b doesn't hit super far behind them it's safe to go for this. Further, you can space out the first hit of nair which will combo into lots of fun stuff like ftilt, utilt, dsmash, up b etc.
You can also use your d throw to bait out airdodges if you condition your opponent to do so beforehand, which you can punish VERY hard with fsmash to get extremely early kills near the edge. Excellent way to end a long tech fthrow tech chase, opponents are much more likely to try to airdodge a dthrow after 3 or so fthrows.
Other than this, jab is often DI'd non-optimally due to the move being relatively quick and/or your opponent trying to DI in near the ledge instinctively to try and survive. It's extremely easy to simply react to bad DI at kill percents with a Blazer. There is no reason to ever just buffer the up b after the jab, there's more than enough hitstun. If they DI properly, just do the next best thing and fair them. But make sure you don't miss your chances for easy kills with the up b in these situations.
During a tech chase/reading their getup option:
Nair hit 1 is more practically used here imo. Any time you have your opponent OTG, you can chase and respond to their get up option with nair hit 1 (sweet) to secure your kills with little risk. Yeah, you can always get a read with fsmash or whatever, but this is often much safer, since the punishment for missing is usually nothing but being back in the neutral stance.
For example, I fthrow Bayonetta at 80 percent. My opponent DI's away because he's been doing this to avoid followups from dthrow and fthrow, and now he can't jump away and must tech. I chase and short hop when they near the ground, and throw a landing nair1 out to cover the missed tech option. Because my opponent is bad, he missed his tech and i hit with nair1, and confirm into dsmash. As luck would have it, I'm near the edge on a small stage and this KO's my opponent. Or if they're 115+ just do up b instead of dsmash. Situations like this tend to pop up a lot when you make your opponent tech. Try it out.
Also, when you have your opponent under pressure, make sure you don't do anything super laggy. As long as you stick to moves like ftilt, jab, dtilt, nair and fair when poking at your opponents shield, you will always have ample time to teach them a lesson with up tilt if they get scared and roll behind you, or to dash forward and grab/attack whatever if they spot dodge or try to run away.