I just did mine a couple of days ago. I agree with Klaus on the clip and o-ring where the line goes into the cooler. I didn't have this on hand and came out okay, but it would be a good idea. You'll need a funnel with a small long end or line to get down to the fill hole. The IPD flush kit i'm sure is fine and I may acquire it at some point but you can get by with a piece of fairly rigid hose available at your local home center that is 3/4" o.d. This fits pretty snug into the hole on the cooler, although it does need to be held in place while the car is running. I did it this way and didn't make much of a mess.

Toyota T-IV fluid meets the JWS 3309 spec/requirement and is around $5.00/qt. at the toyota dealer. I used 16qts on the flush, my car is at 77k and I have no idea on the prior service history. My fluid started running clean around qts. 11-12. Good luck