Does the spell bless weapon work for slingstaff as a sling because of slipslinger style? meaning if I have the sacred keepsake blessed button I get to use bless weapon on the slings ammunition?
Blessed button: "...A halfling who uses it while casting bless weapon on a sling enables the sling to confer the spell’s benefits to the ammunition it fires."
Slipslinger style: "...you treat all ranged and thrown weapons that have “sling” in their name as if they were slings for all feats and class abilities that require such weapons, as well as the warslinger racial trait."
Obs! just assuming spells is a class ability.
Since spells as a class ability do not require such weapons, even while a specific spell might (and bless weapon does not 'require' a sling), I believe they would not count for slipslinger style.