If your bench press is your worst lift and the one you want to improve the most, add 3-4 sets at the end of every workout you do. The reason for this is that the neural adaptations tend to be greater for the last thing you do in a workout. When your goal is to bring up one specific lift, especially if it's been stuck for a while, this should be your go-to strategy.
The minimal load to stimulate rapid strength gains is 80%, so that's the weight you should be using for your daily, end-of-the-workout sets. Use this strategy for at least four weeks. Pick one lift you want to focus on and perform 3 to 4 sets at 80% of your maximum.
The number of reps will vary depending on what you did during the rest of the session. If you did a heavy pressing session, you might only get 2 or 3 good reps with 80%. If you did squats or deads, your upper body will be fresh enough to allow you to get 5 or 6 reps. The key thing is staying at 80% for all of your work sets. Ideally you would not reach failure on any of the sets.
How Does That Work?
This technique works by improving neural efficiency for the target lift. You'll improve intra- and inter-muscular coordination, which will allow you to rapidly gain strength in that movement. Rapid strength gains should be sustainable for 4-6 weeks.
Since you'll hit the focus lift every day, you're bound to have some residual fatigue and you might not feel stronger right away. The gains in strength on the target lift will show up about 10-14 days after you stop doing this strategy. You'll get a big performance gain seemingly out of nowhere!
Note that this also works well for improved muscle growth. One of my figure competitors made very rapid gains in glute and leg muscularity by finishing every workout with four sets of front squats for four weeks.