help with angle iron's

[dbreeze225]

ok ill try...question about sanding i dont have a sanding block.
i have been wraping it around about a inch and a half by 4 inch piece of wood and using wet/dry paper.
i have been sanding aluminum angle (3/4 inch legs) i have been clamping it to edge of table and doing one leg at a time.
the one i did yesterday was about 2 feet long maybe a lil bit longer.
now wraping the paper around the wood i would get 5 strips off one standard sheet of sand paper.
and it took all 5 strips to sand this 2 foot segment.
2 pieces each leg and the the last strip just to touch up everything.
oh and i am only doing the out side of the legs since when they go on you cant see in inside (side down to wood) any way.
to me it seems like i am using ALOT of sand paper it either gets cloged up or looses its grit and i have to move onto a new sheet.
like i said it is waterproof paper and i have been sanding with water. (i was told with metal its better to use water)
am i wrong is this a normal amount of paper to go through?
or maybe i am doing something wrong?