"Frothing at the gash" is an awesome phrase, beaten only by "ploughing" and "putting a young maiden to the sword".
Anywho, I want to nip your initial write up in the bud lest you, or anyone else reading this get the wrong idea (ie that this was a good way to go about your business). Let me dissect the first approach (to the stock pig in the shop), but first, props for getting back on the horse and having another go. This is half the battle.
1) First and foremost, your reasons for wearing the jumper were all out of synch. Wearing something in order to illicit a reaction from people is not a cool thing to do. It's akin to a bloke walking into a place and deliberately flashing his Rolex. It's lame because reaction-seeking behaviour is needy, and women can smell it a mile off. Wear the clothes, don't let them wear you. For a more in-depth discussion, see A-Train's thread from a while back:
http://www.puaforum.co.uk/pua-genera...what-wear.html
2) You made a mistake opening a 5, for two reasons. Firstly, as a less attractive girl, she will be naturally cynical of any guy hitting on her - she is inclined to think you're taking the piss; "he can't seriously be chatting me up, I never get chatted up". It's her problem due to her (perhaps understandably) low self-esteem. This, however, could be overcome had the second reason not reared its ugly head. This being, I imagine (being as you rated her a 5 and said you only wanted to practice) you weren't attracted to her one bit. So there you are, clearly only interested in boosting your own ego by getting a girl to talk to you under the pretence that you're interested in her. She would've sensed it all over you. Hence, she was particularly dismissive. She could've been ruder, I think she showed considerable restraint.
3) Leading on from point 2) - don't think of these people as "practice". They are real people with real feelings, even ugly or fat girls, and deserve to be treated as such. In future, try to concentrate on people you genuinely find attractive - your chatting them up will be a lot more congruent and they will react better. It won't work out the first few dozen times you try to chat them up, but eventually you'll get it. Don't think you have to practice on some uggos before moving on to the hot babes. Not only are they a completely different kettle of fish to deal with, but you need to accept that whilst it'll take a lot of rejections before you get it right, there are loads of babes out there. Don't be worried about "using up" all the hot girls trying to get it right. They're ten a penny.
4) This is a broad point relating to the whole interaction. You felt that you needed to come up with a cool story to show her how awesome you are. Not necessary. In fact, this did you a disservice - you struggled to come up with "decent material" rather than being honest and authentic.
5) A word on negs. Decidedly uncool. I don't blame you for employing one, after all that's the way MM teaches. Most of us have employed them at some point in our pick-up development and subsequently realised our mistake. Taking value from someone with a neg is an inherently low-value thing to do. Bullying is a particularly extreme form of negging, and bullies are at the other end of the scale from awesome, centred alphas.
There. Rant over. Apologies if it was a little harsh, but I'm all about the tough love. Plus I've got my finals on Monday and am obviously looking for every conceivable way to avoid revision. Back to the grind I suppose...