Shaikh Ibn ul-‘Uthaymeen rahimahullah was asked:
Surrounding the subject of smoking, some pharmacies sell medical patches that are placed on the body to give the body what it needs of Nicotine for twenty four hours as steps to stop smoking. The question: if it is placed in the night for twenty four hours, then another placed, does a person break his fast in Ramadan when using it?
“No, he does not break his fast during Ramadan and he can use it. Rather it is an obligation for him to use it if it is a way to stop smoking. There is no harm for a person to leave off something unlawful, step by step because Allah did not prohibit alcohol altogether in one time. Rather he made that prohibition in stages. So first He made it lawful, then He clarified its harms, then He prohibited it in some times over others then He prohibited it in general…”
[Jalasaat Ramadaaniyyah year 1415 H no. 1. taken from the pamphlet here].
So yes a person can stop smoking in stages either decreasing the number of cigarettes a day, the number of times a day, using a Nicotine patch, etc until he quits.
Faisal Ibn Abdul Qaadir Ibn Hassan