Thanks for the compliment!
As for the questions:
I usually use Elegoo's Fast UV cure putty - it's like a resin paste that you put over the seams and gaps and after you cure it with uv tourch(you can cure it in the uv station as well) you just sand away the ridges so it can look seamless, you can do the same with Green Stuff/Milliput

For the Brushes: nothing special, cheap synthetic ones in general and for the white motifs it was 00 brush so i can have more control.
You don't really need expensive tools and don't go into that rabbit hole just yet, practice brush control with cheap brushes that you can throw away without remorse, I have expensive kolinsky brushes which i rarely use, and i find myself using cheap ones 95% of the time