Due to my business I am traveling very often to Shanghai and here are a few pointers to fellow hobbyists, who never have been to China.
Shanghai is a huge city and accordingly has also a big diversity on opportunities for the hobby. Due to language restraints the non-Chinese speaking Foreigner is a bit limited but still then, there is plenty of pussy to go around. The first time in Shanghai I stayed at the Shangri-La hotel. They have a disco in the basement called BATS. If you walk in there alone, you can be certain to have some girl walk up to you and start a conversation. Yes, you are right, it's a hooker. Now here is the first word of advice. Never take the aggresive girls that approach you right away, they are not the best looking, expensive and offer only mediocre service. Settle down and wait and you wil see better things to come. The fun usually starts after ten. Here is what I picked up after finishing a bottle of wine

She quoted me $200 and I told her it was way too much and finally we settled on $100, provided she would stay the whole night. She did and we had such a good time that she took the whole next day and showed me around Shanghai.
Now all the 4 & 5 hotels have bars and sometimes discos and I found that in most places, you see Chinese girls sitting there by themselves and most likely they are hookers. So the easiest way (not the cheapest though) is to check out the hotel bars and discos. Just make eye contact and go from there.
The next best thing after that is the bars in Maoming Lu. Maoming Lu and Julu Lu are two intersecting streets near Nanjing Road. Most bars you just go in and order drinks (there is no cover charge) and then just pick a girl and talk with her. Most speak a little bit of English, some of them very good. I always had a good time in Nelly's Bar, located at the intersection of Maoming and Julu Lu.
Another place to go is Xiantindi where all the Foreigners congregate. It's the fashionable place in Shanghai with shops, restaurants and discos and you can find a lot of girls there too, but it tends to be on the expensive side as it is geared towards Foreigners whereas Maoming Lu is for both Chinese and Foreigners.
Then there are all the Karaoke Bars, where the girls can also be had but this is strictly Chinese speaking territory and most of the girls speak no English.
Pricing can vary a lot. From $70-$200 for the night depending on your negotiating skills and place. A word of caution. Don't go with girls that approach you on the street unless you have all your valuables securely locked away in your room. They will offer you a good price but if you are not careful, they will rob you blind. Another thing to consider as well is that prostitution is illegal in China and if the police sees you making arrangements with a girl on the street, they may follow and bust you in the hotel room. This is also the reason, that some of the girls that you meet, will not come to your room right away. If a girl tells you that she cannot go with you, just take her phone number and set up something for the next day or later onthe same night.
Now the bar and disco scene applies for all big cities in China. I have been to many places in China and found that wherever they have discos, bars and karaoke, there are also working girls to be had although communication may be difficult.