I believe that as a rule the whores bring their own clothes, in fact several changes to see which one the director likes. If it's a higher budget the company may provide clothes.

I notice some girls wear the same outfit for a bunch of movies, viz Nicole Brazzle who wears that same turquiose bikini with matching fingerless gloves. Other girls seem to wear the outfit only once.
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"All my years in p*rn didn't quite prepare me for childbirth. I mistakenly thought all the stretching I did would make this easier."