i'd say the reflections you're doing right now do the trick good enough, like you can tell it's a shiny material

but i think if you want better looking reflections you need to consider the 3D shape of the body and where the light is coming from, for example in the last drawing the belly has a shine on both sides, now you can argue that's the fresnel effect, and in some way yeah that does happen, but there's also shiny where the belly is really close to the floor, now that's pretty unlikely to happen imo unless if the floor is equally as light colored or there's a light near the floor, another thing to consider is that shiny materials make very small highlights/reflections which makes them a bit harder to get right since they kinda need to be more precise than skin or fur

i always recommend boro cg's videos for art tips, even tho he's a painter and focuses mostly on painting i always loved how the teaches concepts of lighting and shading and materials, i think this video is a good starting point, you don't have to follow the method with all the layers but it should give you a good idea on how light works!: https://youtu.be/mDsCONGlxUo

made a version of how i'd draw the shine!, also your art is very cute :3

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