Quick way to convert to christianity?

[Prussian to the Iron]

Fair enough. Matchlocks are a huge benefit, but is there any other way to get matchlocks without converting/Nanban ports?

I believe that you can use matchlock ashigaru and samurai if you go up to "Gunpowder Mastery" in the research tree, but it's really high up and I'm not entirely sure about that. You can definitely get them without converting, while just keeping a Nanban port. The Nanban ports allow recruitment of Imported Matchlock Ashigaru. I think with most factions these take like 4 turns to recruit, but with the Oda, since they are Ashigaru, it takes only one turn to recruit a full 6 units.

[Jungle Rhino]

I believe that you can use matchlock ashigaru and samurai if you go up to "Gunpowder Mastery" in the research tree, but it's really high up and I'm not entirely sure about that. You can definitely get them without converting, while just keeping a Nanban port. The Nanban ports allow recruitment of Imported Matchlock Ashigaru. I think with most factions these take like 4 turns to recruit, but with the Oda, since they are Ashigaru, it takes only one turn to recruit a full 6 units.

Yes you get access to the fantastic Oda Matchlock Ashigaru with Gunpowder Mastery. You also get Matchlock Samurai who are pretty darn good also (less useful for Oda).

It is deep in the tech tree but if you beeline for it at the expense of everything else it won't take that long.