Wood graining a metal front door is not a hard process and can be done by most anyone with a little time and patience.
Start by cleaning the door and painting it.
White will work fine but a light biege may give you more the effect you are looking for.
After the paint has dried for a few days add a coat of stain.
MinWax Gel Stain works the best I have found.
Start with a thin coat and dont worry about being real even just keep the brush strokes in the direction you want the grain to be.
Next take your brush and brush in a rough wood grain pattern. For small items a artist brush works well for larger items use a regular brush.
Take a second brush soft and dry and lightly draw it across your pattern to drag it out and make it look more natural.
Finish off by letting the door dry for several days and put on a final coat of clear finish such as polyurethane.