I don't use a specific brand. I like to try different sketchbooks all the time. I do really like Fabriano sketchbooks. I also like Stillman & Birn books. I think you can email them (S&B) and they'll send you a sample pack of their paper for free. I love Fabriano Venezia sketchbooks and I treat myself to them once in a while, but they can be quite expensive. I find that sketchbooks that have paper with a lot of tooth aren't the most comfortable to draw on with fountain pens ( i guess this would be common sense). Lastly if you can find Hahnemuüle sketchbooks they're very good and usually economical even in larger sizes. I hope that helped a little.
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