However, the tactic can't be "vote Labour everywhere" or "vote LibDem everywhere". That's not a tactic. That's partisan politics.
So if you're advocating either, you're not being tactical.
Don't try to dress partisanship up as a tactic. Because you're cheating yourself - and others too.
Brexit is bigger than party loyalty. If you don't agree, that's fine. But again, just be honest about it.
So for example a Green vote in most seats. That's a political statement. But it's not a tactic. Not when it comes to stopping Brexit.
"Vote for whoever you like, of course. But if it's not for somebody that can help us get closer to Remain, don't try to dress it up differently. And don't try to convince others under false pretenses. Be honest."