Hi my friend @airbum.
Liquified styrene (with MEK as a dilluant) is a great tool for cases like that ugly sink mark on the Jake cowling, or the sealing of the Dakota cargo door or any other situation where you have a gap to fill and give strength to the surrounding area.
Since it's the same material as the model's, it can be sanded nicely to shape.
Care must be taken, as it may create sink marks if applied too heavilly.
You don't have to make it every time before use: you can make some quantity once, maybe a thin and a thick one, kept in jars for a long time no problem, replenishing them on occasion when their level drops.
Jars with brush applicators may be more favourable.
I also like to apply it with a toothpick and, I admit it, wipe smoothly with my finger immediately afterwards...
Once the jar is tightly closed, it can last forever, and if it gets thicker, just add some MEK: so simple!
Here's a video on how to make it:
Th Jake is in good process: fitted the underbelly ammo magazines and belly window frame.
Have fabricated a mini "pylon" to fit there also, as I will not use the simplistic bomb provided.
Painting is delayed due to all these small bits fitting.
All the best, my friend!