Not at all trying to be condescending, but do you have a strong grasp of how the Glock trigger system works? I would strongly recommend taking a bit of time to school up on exactly what all the components, surfaces, etc. do and their functions and how modifications can impact the safety tolerances of the system.
You mention sponginess, and there are two primary stages to a Glock trigger. The first is what I'd call almost a take-up, where the trigger bar's components are actually (further) compressing the striker spring, lifting the striker safety plunger out of the way, and clearing the drop safety shelf in the rear trigger module. Once the rounded, bladed part of the trigger bar contacts the connector, you are into what I'd consider the second stage, where you are further compressing the striker spring, but also driving the trigger bar down due to the angled surface of the connector. Here you are pushing against the connector as well as sliding the searing surface down the striker lug, both of which have friction.
Anyhow, having some idea of what you're trying to solve (and how it can go wrong) will give you some insight. Nothing you can safely do to a Glock will eliminate the need to compress the striker spring, lift the striker plunger out of the way, or scrape the trigger bar along the connector tab and trigger bar searing surface along the striker lug, that's the design. From a black box perspective, you are feeling all that stuff happening as varying resistance as the trigger travels.
The big thing you want to avoid is compromising any of the safety systems, which you can do if you "polish" away any of the material that sets the geometry. Things like "reduced pretravel" Glock triggers can feel way better, but in the extreme case, they can disable two of the safety systems: the striker plunger and drop safety shelf. Furthermore, aggressive "polishing" with a Dremel or file or whatever can alter the geometry in other ways.
Not trying to dissuade you, I feel that it's safe to do a polish job, but have some idea of what everything does so you don't bubba yourself into an unsafe situation.
Here's a quick video that goes over a cutaway model:
View: https://www.youtube.com/watch?v=pThsdG0FNdc
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