(Skip to Step 3 if you want to create a "Strange Genuine Professional Killstreak Righteous Bison" or a "Strange Unusual Professional Killstreak Horseless Headless Horsemann's Headtaker")

Step 1: Obtain 200 copies of the unique variant of the weapon you want to create.

Step 2: Aquire the correct collector's chemistry set for the weapons, and use all 200 copies to create a Collector's variant of the weapon.

Step 3: Aquire the correct strangifier chemistry set for the weapon, and insert all the proper items to create the strangifier for the weapon.

Step 4: Use the crafted strangifier on the weapon to apply the strange quality to it.

Step 5: Aquire the correct professional killstreak kit frabricator for the weapon, with the sheen and effect you want, and insert all the proper bot parts to create the professional killstreak kit for the weapon.

Step 6: Use the professional killstreak kit on the weapon.

If you don't like gathering all the parts for crafting, you could just buy or trade for the strangifiers, professional killstreak kits and base collecter's weapons. You could also outright buy or trade the final product, but that takes the fun out of it.

The following weapons are available in "Strange Collector's Professional Killsteak X" quality:

-Pretty Boy's Pocket Pistol
-The Cow Mangler 5000
-The Air Strike
-The Righteous Bison
-The Phlogistinator
-The Manmelter
-The Third Degree
-The Widowmaker
-The Pomson 6000
-The Vaccinator
-The Classic
-The Cleaner's Carbine

The following weapons are available in other qualities than "Strange Collector's Professional Killstreak X" quality:

-The Righteous Bison (Strange Genuine Professional Killstreak)
-The Horseless Headless Horsemann's Headtaker (Strange Unusual Professional Killstreak)