Can an Unusual weapon be made a Strange Professional Killstreak weapon?

You can make an unusual weapon strange and killstreak if you have a strangifier and a killstreak kit that match the base item type.

You can't change a weapon's paint, so you need to start off with the unusual painted weapon you want.

There are quite a few cases in which it won't work though:

• Not all war paints have unusual versions obtainable.
• Not all war paint weapons have strangifiers available for them.
• Not all war paint weapons have killstreak kits available for them. (I'm not actually 100% sure on this fact, and we might be able to still find generic killstreak kits for extremely high prices that apply to any item.)

Here's an example of one for sale that's Killstreak, Strange, and Unusual:

Note that it had to have started off with that war paint and effect since it was unboxed.