Every note in the blues scale gets bent all the time. Although we almost always bend up, we can increase the tension of a bend by approaching the target note, but not quite reaching it (which is hitting it flat.)
In order to get the hang of this, practice octave double bends on the top two strings.You hold a note with the index finger on the first ring and then bend a note on the B string with your third or fourth finger until they are in unison. you can get the sense of how much tension is created by not pushing all the way up to the target simply by stopping short.
The third and seventh are only flat relative to and clash with major and dominant progressions. Only the flat five retains its tension in minor over the I-7 chord.
This is all a vast oversimplification because the blues scale is always played on the root of the key, not chord, so as the chords change so does the sound of the scale, and the notes you are more likely to bend also change. So be prepared to bend them all.
To be honest, however I believe most of the times you have a poor string bending sound it is because the player fails to use wrist rotation to power the bend instead pushing straight up with their fingers which makes a very lame sound. Also the string resists you in the upward part of the band yet it pushes you in the downward part called the release. so turn up and let the string push you back down to create an even bend and release.
Remember we are used to hearing the variable acceleration of the wrists circular motion pushing the string. The pitches are easier to spot when they ramp up properly.
Be very wary of Wikipedia. Btw the 7 and 8 note blues scales on it are bogus and yes I read all the articles they cited.