The Ibanez uprights looks really good, but you can still translate a lot of BG technique directly to them, whereas once you go full scale you'll need to change things with both hands.
For left hand, definitely worth starting with Simandl technique (you don't need to wade through the whole book, but get used to the fingering). For the right hand, watch some videos on the technique there as it's a lot more "vertical" than BG. You _may_ be already doing this on the Ibanez but most videos I've seen involve the players aligning their fingers more horizontally (like a BG turned on its side). For full scale you need a lot more meat under the string so even if you can get notes with the horizontal plucking it won't sound as good.
In terms of playing with others, I'd start simple with lines that you can play down the bottom of the neck, and bring another bass so you can change when you get tired rather than risk injuring yourself. It won't take long for you to start enjoying playing the thing....