As Trump goes to the continent, these would be my recommendations.
First, he cannot show hard-line nationalist support. If he does this during his visit to Brussels, America stands a lot to lose diplomatically. He is not a tool of the Right, but he is likely viewed as a tool of the Right, and he has to actively work to undermine these perceptions. He can do this by showing a commitment to civil liberties, which as a New Yorker, shouldn’t be so hard to do.
Second, he cannot show Russian support. Not only will this inflame the current inferno, but any wink/nod that really we are all on the same team will actively undermine liberty, promote fear, and further give way to Russian-style Network-Authoritarianism on the continent. As much as he might think he can tell Brussels one thing and America another, he can’t. This will not appease anyone.
Third, he needs to lean on Brussels to take a lead in diplomacy with Islam, while reiterating support for NATO, especially in a war on terror, now centered on the continent. He should also work with the Vatican in this direction, while assuring them that the crisis in the American Church is over.
Trump has been at a continuous stand-off with the press in America, but in Europe, where they more readily see him for what he is, this will not fly. Trump never does it, but the time is now, to drop the con and speak from the heart about Liberty under God. There may be no other way.