Noses come in all shapes, sizes and colours. In my opinion, the fundamental skills to learn as an artist is perspective, lighting and shading... almost anything can look good with great lighting and shading ;)
I normally do most of my painting on a single layer. Don’t get discouraged in the initial stages when it looks rough, it only matters what it looks like when you’ve finished :)
There is no ‘right’ or ‘wrong’ way to go about it. Have a look at other artists techniques and adopt one or adapt to suit yourself, it all comes with practice.
I pretty much use a single brush in Photoshop, just the soft round brush, but vary the size and pressure using a Wacom. This painting however, I started experimenting with a ‘splatter’ brush to give a little texture, which is required especially when painting men or the elderly.