Help with merging two WADs

Hello fellow Doom fans.
I am new to this site, but have been a huge fan of DOOM for years.
I enjoy playing invasion WADs, but i want to add the cool weapons and sprites from WADs such as Brutal Doom, or the Modern Doomfare (realistic guns wad). For an example of a WAD combination I would like to play would be Armageddon Invasion wad and Modern Doomfare. If anyone can provide some assistance, I would be more than grateful.

Thanks,
Will

I assume you're using Zandronum.

Start up Doomseeker, start a custom server, load Armageddon and Modern Doomfare into the custom wads box, and then play offline.

Thank you for the reply,
but when I tryed the amerageddon wad with the modern doom fare I seemed to get a fatal error . When I tryed again with brutal doom, the fatal error occurred again with the message, "avoidmelee" is an an unknown flag.

Someone with more knowledge on the mods will have to clarify, but it's possible that the two mods are incompatible with each other (ie. both make some sort of change to the same thing, and so the engine can't know which "change" to load, if that makes sense).

Thanks for the additional information , you where 100% correct; because I tryed the instructions from the first reply with Skulltag this time and it worked!
Once again, I appreciate the help.