Fortunately I have done this before, so I know I set off running, and get a few characters going, but the plot then seems to idle. One of the reasons is not wanting to suddenly find oneself at the end too soon.
If you write in summary form (I'll pad this out later) then it proves all too easy to just close out.
I notice that I do third-person descriptions of the story, which seems like 'telling rather than showing' and always needs fleshing out.
Dialogue can prove a safe way to get from page to page, although quite often it is not moving the plot along, but just people chatting. That can work in context (think Pulp Fiction):
Vincent: And you know what they call a... a... a Quarter Pounder with Cheese in Paris?
Jules: They don't call it a Quarter Pounder with cheese?
Vincent: No man, they got the metric system. They wouldn't know what the fuck a Quarter Pounder is.
Jules: Then what do they call it?
Vincent: They call it a Royale with cheese.
Jules: A Royale with cheese. What do they call a Big Mac?
Vincent: Well, a Big Mac's a Big Mac, but they call it le Big-Mac.
Jules: Le Big-Mac. Ha ha ha ha. What do they call a Whopper?
Vincent: I dunno, I didn't go into Burger King.
My baddies have started evolving, but they don't seem mean enough yet.
I think I need to do more sensual descriptions, to clarify who people are by the way they look, and dress, rather than just what they say, and think.I also need to evoke Seville more warmly, with the weather, the customs, the huge variety of bars, the food, etc.