I have had a number of pencils in my craft kit which have been less than perfect. Do make sure your HB pencil is not 'scratchy'. Some pencils I have used 'snag' as it is pulled over the paper; you would be advised to make sure the pencil runs smoothly.
I have been a fan of the mechanical pencil ever since my student days started in 2000 when i learnt the benefit of not wasting time sharpening pencils while note taking. When it comes to crafting mechanical pencils have two benefits: they come with an eraser attached and the lead is retractable therefore does not mark any papers left in your craft-box.
It is however a personal choice and a standard HB pencil is all that is needed.
You also will need to have an eraser, some of
those smudge, can also be a bit scratchy or poor at erasing. I am fortunate that the pencil I use comes with a lovely soft eraser which does not leave a grey smudges when i use them.
If i did not use the eraser attatched to my pencil I would use an artists 'putty eraser' or another quality eraser which left no marks. These kind of erasers are found in art shops, craft shops and large stationery stores.
Other erasers are likely to come in cheaper, but as at January 2012 a putty eraser is between £1 and £2 depending on the make and the supplier.