For new models, I'd agree with
@dark_mermaid that it's probably best for them to keep PM's on. In some ways, the pain of managing them is a good first experience. But, I see no reason why a model couldn't quickly turn them off on her second or third broadcast if it gets too bad. Then, in the topic, whiteboard or charlebot messages say something about friend add/PM for a token amount. Even if just 25 or 50, it'll keep some at bay that otherwise just want to waste time.
I agree with
@WickedTouch with what he said. As a member on MFC, I view PMs as a privilege, as I don't want to distract the model from the room since I'm not the only there to see her. I generally like to type in the room, unless it's something that I'd rather not be public. Usually, a 5 token tip note does it and if it piques the models interest she'll comment or send a PM. If I want the model's attention exclusively, that's what TruePrivates are for.
Regarding models PMing right away, there's another discussion on PM's in a different thread also. But, here's how I do it:
I have my PM's blocked to friends and bookmarked models only. Model friends are those I visit frequently. If there's a model I want to check out, but haven't been in her room before I will add her to bookmarks. This allows her to PM me, whether when I first enter the room. Or, after a tip or some time in the room. I view it as I'd rather give her the opportunity to reach me privately instead of say it in the room. It's her room, so want to extend the courtesy to her. If I don't like her, and no plans to revisit the room, I can delete from bookmark and leave.
This is how today went for me. There was a model I had seen online numerous times previously. But, never visited her room. Prior to going into her room, I added her and then entered. Observed for a couple of minutes, and sent her a private and silent tip with a note saying hello and that was my first time in her room. She smiled and thanked "ninja" for it. Over the twenty minutes or so I was in her room, made a couple of public comments as well as a couple more tips w/notes letting her know that I enjoyed her room and such. Every time, she smiled and thanked "ninja" for them. At one point, she commented that members need to chat in the room since she doesn't pay much attention to PMs. After my third tip, she sent me a PM thanking me to which I did a quick response and we had a couple of back and forth messages and I left it at that.
Had a great time in her room, and let her know via tip as I was leaving. I think had I of not allowed her to send a PM, things might have been a little different. I'll keep her in the bookmarks for at least a few more visits. It allows me to interact with her if she chooses to initiate it. But, it also allows me to see how she is as a model and a person before bumping her to friend list and more frequently visiting her.
I generally don't mind if a model PM's me a "Hi!" or other similar message when they see me online. But, when I get PMs from numerous models begging me for tokens or to visit their room, that's why I block all but those on my lists. The models on my list have proven they aren't as annoying to me as many other members are them. Maybe I'm wrong. But, in a sense I feel like a mutual level of respect has been earned on both sides.
Apologies for the long winded response.