Beginners may want to start by having their partners massage or apply pressure to the anus. The tip of one finger can then be inserted slowly. If the receiver is relaxed and finds it pleasurable, more fingers can be inserted one at a time. Sex toys that slip over the fingers may be used to replicate anal fingering if long fingernails make fingering dangerous.
Prostate owners will usually find anal fingering particularly pleasurable because it can lead to the stimulation of the prostate which is the equivalent to a G-spot.
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Lubrication and a gradual buildup is the key to making anal fingering - or any other anal stimulation, for that matter - pleasurable for all parties involved. Use a water-based lubricant and start out very slowly at first.