The first and most effective way: first, carefully straighten the wire with your hands, place it on a level and solid surface, like a table, then put it on a metal bar or other smooth and solid object. Roll it on the table so the wire is moved, pressed against the brick. After several such passages, you can achieve very good result.
To straighten soft wire, one end into the Vice and clamp, and the other insert in the Chuck hand drill. Do the drill a few turns, and the wire will quickly straighten out.
You can use simple home-made device: a small crack in a plate a few nails at a distance below the wire through them passed with difficulty. Then pull the wire between the nails several times. You will quickly get the desired effect.
A traditional method. Short pieces of wire put on a solid, preferably a metal surface and tap on the bend with a hammer, and then pull it under the wire. Iron or aluminum wire you need to straighten the metal with a hammer, and softer, such as copper — with a mallet.
You can also try to use the following technique: tie one end of a long wire to the door handle, and then strongly pull it out with pliers. Then cut need, the most straight cut. You cannot bind the wire to loose subjects, for example, to the battery.
You can also take a fairly long tube, the diameter of which is slightly larger than the cut wire, and then gently stretch through it. If a suitable tube at hand is not, drill a hole the right diameter in a thick piece of wood and pull the wire through it.