I've made sushi with long grain rice - it is possible, but I would suggest finding a short grain rice to use. I get mine at the Asian market and I think it's well worth it. I use Nishiki sushi rice - it works for me...
Making sushi rice is a process. There are directions on the bag, but if you follow mine you'll end up with perfect rice every time.
Just so you know 1.5 cups of sushi rice will turn into a bit over 6 cups of rice when it's cooked.
1.5 Cups Sushi rice
2 Cups Water
2 Tbsp + 2 tsp Rice Vinegar
1 Tbsp + 1 1/2 tsp Sugar
1/2 tsp Salt
Take 1.5 cups of rice and put it in a fine mesh strainer. Run the rice under water until the water runs clear. You can do this in your pot as well. Put the rice in the pot and fill half way with water. Run your fingers through the rice and the water will become a milky color. Drain off the milky water and replace with fresh water. Keep doing this until the water is clear again. Once you get the rice washed drain it as well as you can, then let the rice sit undisturbed for 20 minutes. It's amazing how white it will become. Add the rice to a pot and put in the water. Cover and bring to a boil. Once you are on the boil reduce the heat to low and let cook for 20 minutes.
Once your 20 minutes is up you need to cool the rice down quickly. If you don't have one of those fancy wooden tubs - a large plate will work just fine. Carefully spread out the rice and start fanning it with a hand fan or I used a magazine... Fan the rice for a few minutes then sprinkle on the vinegar solution. Cut the vinegar into the rice - do not stir the rice slide your spoon or spatula through the rice to mix. You want the rice pieces to stay separated not a huge mushy mass... Continue to fan the rice while you are cutting through it. Turn the rice over and continue to fan. After about 5 minutes the rice should be ready to use. You can store the rice under a moist towel until you are ready to use. I like to put mine in a plastic bowl and cover it with a damp towel... You will need to moisten your hands before working with the rice. It's really sticky!