Transmission Issues + Lucas Slip Fix

Hey Everyone,
This question is not Tacoma related, but I have met some really knowledgeable people on here and maybe y'all could help me out.
My brother's GF has a 2005 VW Beetle. The transmission is slipping hard in 2nd/5th. It is a 6-speed Automatic 2wd Fwd transmission.
I had to pump out a quart of transmission fluid (love sealed transmissions), and I put 12 oz of transmission slip-fix (lucas) and 16 oz of ATF designated for the vehicle.
I have not started the vehicle yet because the battery is dead. However, I was reading that it must be added to a warm engine, because the lucas slip stuff is so thick that it will just get stuck to the bottom of the pan. Again, I added it to a cold engine.
Any validity to this? I told my brother to just start the car today and let it warm up for 15 min and drive it around and see if that fixes it.
Do you all think that the trans slip-fix is fine being put in there on a cold engine? Should I drain it and add another 12 oz's too a warm engine? Or can they just drive it at this point after 15 minutes and the transmission fluid should be in the proper areas to start doing it's thing?
Any help would be greatly appreciated!!

 

Eventually, due to the heating up of the fluid, the Lucas additive will circulate with the fluid. The point of adding it warm is to allow the up to temp fluid to help flow the additive, and also to prevent clogging up internal filters.