Controlling Senses by Devotional Service

SB:1.10.23:
Lord's transcendenatal form is perceived by those who have purified their mind of all material consciousness by dint of rigid devotional service and fully controlling their life and senses.
       - Senses can't be artificially controlled. Eg: Vishvamitra Muni. They need engagement. Devotees, by engaging the active senses in the devotional service, prevent them from being allured by inferior engagements. BG also confirms : Senses can be controlled by only better engaements. This is the only and easiest means of sense control.
       - Sense control is possible only when mind is freed from material desires arising from material consciousness. Anything engaged in devotional service is purified of material contamination. Material contamination is due to ignorance only. To one engaged in serving the Lord, by His grace all factual knowledge is revealed within the heart and thus, the darkness of ignorance is dissipated.

So devotional service not only necessitates engaging the senses in the service of the Lord but also purifies them of material nature. By serving Hrshikesa, the master of senses, senses are spiritualized and then one can attain liberation.