Here’s a script that takes all the spot colors in your Swatches palette and generates a user-specified number of gradations - ie, tints from 10% to 90%, or whatever increment you choose.
Enjoy!
Luke
tell application "Adobe Illustrator"
set the_number to text returned of (display dialog "How many gradations per spot color?" default answer "10") as integer
set the_step to (100 / the_number)
set myDoc to document 1
tell myDoc
set the spot_list to (index of (every swatch of it whose class of color = spot color info and name ≠"[Registration]"))
repeat with tint_me in the spot_list
repeat with i from 1 to (the_number - 1)
make new swatch with properties {color:{tint:(i * the_step), spot:spot of color of swatch tint_me}}
end repeat
end repeat
end tell
end tell