I have tried to find a white pen. Gelly pens - hmmm...ok but can't get them to work sometimes. Tried Permaopaque because I love what Effy Wild does with it in her Book of Days class. It worked but as the name implies - opaque effect and I wanted a bright white.
Went to the local art supply store and found the Sakura Pen Touch -- LOVE it! Didn't take long and I had bright white outlines on my journal entries. It does act like a paint pen. If you have used them you have to shake it and then push the nozzle up & down a few times to feed the paint down. Once you do that I have had no issues.