Incidentally, this is probably an oversight/bug -- since other ammo types (project id 20-25) are excluded from being able to raise smithing/artisan skills, presumably to avoid this "easy to spam" effect:1.) Crossbow bolts. Produce them one at a time. Their materials are dirt cheap and they are produced fast.
Code:
<<if $addey lte 18 or $addey gte 28>>''Your Blacksmithing skill has increased (+1)!<<set $blacksmith+=1>><</if>>
<<if $addey lte 18 or $addey gte 38 or $addey is 30>>''Your Artisan skill has increased (+1)!<<set $artisan+=1>><</if>>