X servers may have a limit for the maximum cursor size, especially if they use a hardware implementation for the mouse cursor. Others do not have such a limit. E. g. XF86_S3 3.3 works even with a 512x512 mouse cursor (rather slowly).
The magnified cursor font must have the same name as the original font (the font name must be cursor, file name does not matter)—that is no problem as bdfresize does not change the font name.
The directory with the new cursor font must be placed before the directory with the standard cursor font in the the font path—this is accomplished with xset +fp (as opposed to xset fp+).
Changes in $HOME/fonts/ will be visible only after the command mkfontdir $HOME/fonts; xset fp rehash and only in newly started X clients (more exactly: for newly created cursors).
xset +fp path may not work on a X-Terminal. In this case a font server (see the section How to use a fontserver) can be used if supported by the X-Terminal or some other method to install the font on the X-Terminal (this can generally only be done by your system administrator).
The same approach can be used for olcursor and decw$cursor fonts and any other cursor font you may encounter.
Cursor fonts produced by bdfresize don't look smooth, especially at larger magnification factors. It would be nice if someone could create better looking handcrafted version at some common sizes.