If I remember right, there was a Virtual keyboard used in IR-Shell, which could be a helpful sheme here.
If you hold the right stick down, you have to press one of the other/reachable (so X, O, TRIANGLE and SQUARE are a bad choice, since you hold down the R-Stick...) buttons.
Same for the other directions, up, left and right.
i.e.: Hold R-Stick down/up/left/right and press one of the directional-buttons on D-PAD, to type a letter/character.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux