When playing 11th chords, a particular problem arises because the 11th degree is the same as the 4th and this clashes with the 3rd of the chord which is only a semitone distant. This is particularly noticeable when the chord played by a harmonic instrument is in the same register as the melody player's 11th.
When playing suspended triads and seventh chords, the 4th replaces the 3rd, so there is no clash. However, when playing 11th or 13th chords, the 11th degree is either sharpened by a semitone, or omitted from the chord. In minor chords, the 11th does not need altering, because it is already a whole tone away from the flattened 3rd degree and therefore doesn't clash as much.
Here is an improvised line created from the notes of these two chord types.
Now try this progression which uses #11 chords amongst other chord types.
This solo played over Rhythm Changes uses substitutions at various points. On the recording it is played fast (mm 3=220), but learn it slowly at first. Once you learn a phrase, make up your own variations on it as well as improvising over the Rhythm Changes Jam- Along track on the CD (page 221).