I honestly just avoid talking about it. I usually talk about 'being heavily medicated' or something to the effect of 'I'm a legitimate crazy person'. I've found it makes most people uncomfortable to talk about mental health so they change the subject, or laugh it off as a joke.

In most situations, I won't lie about it if directly asked, but as you pointed out, I feel like I need to explain the differences for like 10 minutes if I tell someone I'm BPII.