The tutorial in text:
I will show you how to make a bucket-hat on a citizen like this
1, First place a npc_citizen
2, Give the "npc_citizen" a name
3, Now place a "prop_dynamic_override"
4, Find the model you want (i will use a bucket)
5, Now place the bucket ("prop_dynamic_override") on the head of the "npc_citizen"
6, Give the bucket ("prop_dynamic_override") a name
7, Go to "OutPuts" in the "logic_relay"
8, Use this OutPut: "OnSpawn-(name of the bucket)-setparent-the name of the "npc_citizen")
9, Now add this OutPut: "OnSpawn-(the name of the bucket)SetParentAttachmentMaintainOffset-mouth" and then add a delay of 0.01 (very important)
10, Now Youre Done!!