If you use an inkjet, you’ll need to either find a waterproof ink or you need to pre-age the paper if you use a wet coffee process. Otherwise, as you’ve unfortunately found out already, it’ll make a normal ink bleed on the page. Best bet is to stick with a laser printer or photocopier (something with toner).
If you do pre-age the paper, be sure to get it really really flat before you feed it through the printer or else it can lead to jams. (I know this from many many instances of it.)
I'm at the point where I'm about to weather/dye the pages of my diary. I used normal print paper, but used a laser printer so the toner would bond. I see numerous tutorials on using coffee/tea/thinned paint to dye the pages. Anyone want to chime in with a tutorial they prefer? (hopefully cut some trial and error out of my process?)
The video above is a great inspiration, I wish is had just a few callout to guide us better, like the weathering solution recipe that is in the cookie sheets.
Thanks anyone of your folks who have done this before for guiding me -- I have 16 signatures ready to go, feel a bit impatient but also scared to screw them up.