They are correct. Like I said above, don't weld in the same spot, 2 inches only. With the bondo I use a golf ball sized thing of bondo and a pinch of hardener the size of the tip of your pinky finger to that first joint in it right behind the finger nail. Same with the baseball size hambiskit said about. Evercoat makes a bondo called Liteweight. It is almost as good as Rage filler and cheaper on the price a bit but works EXCELLENT! First put your bondo down, let it dry some and when it is almost dry but still a bit soft then you can use a cheese grater. If you don't have one of these (Not an actual cheese grater, a body tool one) then you can let the bondo dry up for a little bit and come back over it with 80 grit. Reason for 80 grit is to CUT the bondo down, anything with less grit wont cut down, it will smooth it and leaving the bondo all wavy. After 80 I use 160 or 240. Anywhere in there is fine to smooth it down. A lot of people use different things. I learned how to do a lot of this kind of thing from SprayTech here on the boards. After the 240 you can do your 400 grit and lay your primer or whatever you plan to do. Get yourself a quart of Evercoat metal glaze. It is like bondo and really thin and watery but it fills in pin holes and SMALL imperfections. Not completely needed but it's only 19 bucks so worth it. Make sure you use the correct amount of hardener in this stuff or else it stays a bit mushy or soft. The bottle will tell you how much to use. After all that sanding and bondo is done then get you some wax and grease remover and prime and paint that thing!!!
Good luck!