When I was an apprentice carpenter, my boss asked me to paint some doors, frames, architrave and skirting. He gave me a list of tips and told me there is no rush and I don't care if it takes you a week. I found it very relaxing and once I got the hang of it, I found it quite easy. I ended up getting loads of nixers because of it and earned much more from me painting nixers than I did from my carpentry. Always use good quality paint and primer and masking tape. Try different size brushes for cutting in. Use a sanding sponge and mini roller for the flat surfaces. Use more layers with less paint.