What aids intercourse is also generally what aids masturbation when it comes to this: lube for both is must about helping protect the delicate tissue of the genitals and make movement more fluid.
So, you can get and use lubes in the aisle where condoms and the like often are: all of those are as suitable for masturbation as for sex with partners. Alternately, since you don't have to worry about anything like condom integrity (or, if you have a penis and not a vagina, vaginal irritation or imbalance), you can opt for lubricant that isn't latex-safe and is safe for your body and effective, like coconut or other vegetable or fruit oils. Some people use body lotions for masturbation as well, though you'll want to go for unscented types with that to avoid irritation.
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