You start by changing how u view passing chords. Contrary to popular belief, passing chords are NOT a separate box of chords. They are just regular chords used that aren't part of your basic progression pattern.
Next, you look at your basic progression pattern. Find the spots where u stay on a chord for a while. Look at those chords and the chords that follow them and see if u can throw in some logical chords that connect the 2 together. Example:
1-4-5-6-7 progression
Key F LH/RH [4/4 time count] 60-70bpm
[1,2,3,4] F / C-F-A
[1,2,3,4] Bb / F-Bb-D
[1,2,3,4] C / G-C-E
[1,2] D / Bb-D-F
[3,4] E / C-E-G
*the numbers in parenthesis are for the tempo
Now, look at the first 2 chords. You see how u stay on the 1st chord for a full count. Well, why not add a chord there instead of just staying on that a while.
Your next question is probably: What are my options? To answer that question, u need to know what chords resolve or lead to 4. Here are some great options:
Options Set #1
1 dominant type chord (7th, 9th, 11th, or 13th)
1 chord with the 3rd in the bass
#4 chord, *a chord 1/2 step above ur target chord
So, now that u got ur options, plug each one in and see if u like the sound:
[1,2] F / C-F-A
[3,4] F / C-Eb-F-A *added Eb to make an F7 chord
[1,2,3,4] Bb / F-Bb-D
[1,2] F / C-F-A
[3,4] F / A-Eb-G *added Eb and G to make an F9 chord
[1,2,3,4] Bb / F-Bb-D
[1,2] F / C-F-A
[3,4] F-Eb / Bb-Eb-G *added an Eb major chord to make an Fm11
[1,2,3,4] Bb / F-Bb-D
[1,2,3,4] F / C-F-A
[3,4] F-Eb / A-D-Gb *added a b9 and a 13 to make an F7 b9/13
[1,2,3,4] Bb / F-Bb-D
[1,2] F / C-F-A
[3,4] A / C-F-A *1 chord, with 3 in the bass
[1,2,3,4] Bb / F-Bb-D
[1,2] F / C-F-A
[3,4] B / A-Db-Eb-F *chord 1/2 step higher, B9 b5
[1,2,3,4] Bb / F-Bb-D
[1,2] F / C-F-A
[3,4] B / A-Db-Eb-G *chord 1/2 step higher, B9 #5
[1,2,3,4] Bb / F-Bb-D
Look at that, u got 7 options right there. And u can even vary the rhythm in which u play those chords. U can bring the passing chord in on beat 2 or beat 3 which gives u 14 more options, for a total of 21 passing chord options right here.
Something else u can do is see if u can add in a passing chord "move", meaning playing more than one chord. Knowing theory here is good. The ZIP CODE IS: (7)-3-6-2-5-1-(4)
Now, using the 1st two chords of this progression example, u have a 1 going to a 4. But, right before u get to 1, u have a 5, a 2-5, a 6-5, a 6-2-5, a 3-6-2-5, and a 7-3-6-2-5. Judging by how much time u have in between chords, u can choose either one of those options to play with your 1 chord then go to 4:
Options Set #2
[1,2] F / C-F-A
[3] C / Bb-Eb-G *5 chord, Cm7
[4] F / A-Eb-G *1 chord, F9
[1,2,3,4] Bb / F-Bb-D
[1] F / C-F-A
[2] G / B-F-A *2 chord, G9
[3] C / Bb-Eb-G *5 chord, Cm7
[4] F / A-Eb-G *1 chord, F9
[1,2,3,4] Bb / F-Bb-D
[1] F / C-F-A
[2] D / C-F-A *6 chord, Dm7
[3] C / Bb-Eb-G *5 chord, Cm7
[4] F / A-Eb-G *1 chord, F9
[1,2,3,4] Bb / F-Bb-D
And the list goes on and on. Like I said ealier, u can experiement with the rhythm on these chords to make even mor options. U can come in on the in between beats as well:
[1,2] F / C-F-A
[an] G / B-F-A *2 chord, G9
[3] C / Bb-Eb-G *5 chord, Cm7
[4] F / A-Eb-G *1 chord, F9
[1,2,3,4] Bb / F-Bb-D
Now, after u have found a passing chord or passing chord move that u like, WRITE IT DOWN AND TRANSFER IT TO EVERY KEY. This way, it becomes a part of your music and then u won't even view it as passing chords. U will view it as a progression within itself.
This is how the pros do it. They practice these moves over and over and over again until its a natural part of their music. You can do the same thing. If anyone has questions about what I've posted, feel free to ask!
