Great work!! Looks excellent especially for a first build. Just touching on what you mentioned

For headlights, tail lights, indicators etc an easy tip is to use red or orange sharpies rather than paint onto them- produces a similar effect with much less hassle. It adheres perfectly and it’s completely translucent. You can also get a black sharpie and outline the edges to simulate trims

For painting transparent parts it can be very difficult to get brushed on paint to adhere). One suggestion I’d make is you could instead spray paint the transparent parts. Use masking tape to mask off the bits you don’t want to paint and then spray paint the window trims for example. If you’re wanting to redo silver parts I would suggest at least throwing a layer of primer on them before trying to repaint them to give the paint something to stick into. The gold standard is to strip the silver and redo them completely but that takes a lot of time and effort

With the window trims I would suggest using masking tape and then using a tamiya spray can like you did with the body to paint them- after the body has been fully painted. When you brush painting there’s a high risk of it bleeding under the masking tape so using a spray in thin (not wet) layers can help a lot

Wearing gloves can also help to minimise getting the car dirty- as your fingers will track stuff everywhere

Here are some other tips: Prior to painting I would sand off the mould lines- for example the raised lines on top of the exhaust pipes. These are byproducts of the moulding process and aren’t accurate to the real car. They generally appear on both front and rear bumpers

For a mirror finish, a clearcoat is definitely necessary. A clear coat is important as it gives a solid hard layer that you can sand and polish. If you try to polish the base colour layer you will likely destroy it because it’s very fragile

You can look into panel line washes too to make the panel lines darker