Don't know about these paint applicator pens...

These applicator pens do not seem as useful as expected. Other than being a repository of large, unpredictable dollops of material, the pens may be useful liquid holders.
When you press down on the vertical applicator tip to get some coating material, it gushes out in very unpredictable, excessive amounts.
If the drops of paint happen to fall on a clean, non-absorbent surface, you may be able to take a tiny artists touch up brush and dab it in the blob amount of paint that goes on the substrate.
Otherwise, if the big drop of excess paint from the paint pen falls on your fender or new Nike Crossfit shoe, please find some Acetone quickly.
Maybe with the tiny artist brush, you have a possibility of applying the correct amount of material.
The removable tips of these pens come out very easily They are easily dropped.
Then, when you wipe off the inevitable excess paint, the fiber tip will inadvertently get pulled out and fall on the dirty garage floor and becomes junk.
Best case, those little tips appear to be one-use only.
Even, if the contents of the pen are barely used, the pen goes in the trash if the removable tips are dried up or otherwise compromised.
My recommendation would be to get your touch up paint in a little unpressurized container that will enable the user to select application method and size of applicator appropriate for the application..