I have read newspaper articles where the decoy turn down men who just asks for massages or modeling only. If you talk about specific sex acts, you are manifesting intent. Never say anything sexual.
When you come to the room, tell them your back is sore and would like a massage. Undercover decoys are not going to waste time massaging you. They are not expert in massage and they can get into trouble doing it.
Most likely will never come to arrest because the decoy will most likely not book an appointment based on your intent is massage or modeling only.
It is possible to still get arrested but they will have to release you or dismiss the charges. If ask about nude massage, tell them you are not interested in nude massage.
Since escort services are not defined, you can ask for these services. It is not a crime. If you going to take a photo tell the escort you will not photograph her face and she can cover her face before the photo session. Most escorts may be self-conscious of their face being shown. Make sure you state that over the phone.
Why is it easy to arrest Johns or hobbyist at a Backpage.com sting operation? Many of these men do not have the knowledge, experience, and are newbies. Police do not have trouble finding these men to sting.
If you need some other ammo to beat the sting operation, ask them if they do domination.
You can ask the escort to say sh*t to you for a fee. It is not a crime.
The decoy will try to move the conservation to get you admit something sexual. Never admit to it, say that you offended, and leave. Don't even say No. Tell them that you are not into these illegal stufff.
http://www.youtube.com/watch?v=V7bGemxByEE
These men are about getting down to sex in a hurry. It is not all about the sex. It is companionship.