You cannot reflect on an odour linguistically; you cannot move it into some mental workspace and manipulate it to the same extent as you can for sound and vision.
Yet certain odours can trigger intense emotions and associated memories and, despite my warning about overdoing the madeleine effect as a cue for flashbacks, smells have an important part to play in our writing.
Some novelists have used smell as a motif throughout, to powerful effect. In Andrew Miller's Pure, the smell of rotting corpses is ever present – not a book to read if you are feeling at all queasy. In Alison Moore's The Lighthouse, the protagonist is obsessed with the perfume of his long-lost mother, which he tries to recreate in all kinds of ways.
In the fourth of my June short stories (yes, I know it's now the end of July), A Smell of Paint, a mother awaits her artist daughter's homecoming, gradually coming to realise that the lingering odour in the newly decorated bedroom is the least of her concerns.