One of the first things I do is cut eight lengths of solder (make them longer than you need). I then roll them between two hard and flat surfaces (I use two pieces of thick glass) to get them straight. I've found it's easier to start with straight pieces. And if a bend goes wrong (and it will), just re-roll the piece straight. To me the most difficult thing is to get the engine block firmly attached to the frame but still removable when done. That engine needs to be secure while you are doing all the fitting so everything lines up in the end. As I said, it's really not that hard.