500 bullets and 2 lbs powder might be a bit over committing if the combination does not work. You might want to go with 50 or 100 bullets and 1 lb powder. You can start with a starting load then work up in .5 grain increments until you find the 'sweet spot'. From there you can fiddle with primers but if the load is good, don't bother. The other method, as described by JR Sundra, is to use a few powders and shoot 3 rounds up to recommended max in 1 grain increments to establish the max load in that powder. For example, if 58 grains is max for a certain cartridge/bullet weight combination you would load and fire 56 grains, 57 grains, 58 grains. If you see pressure signs at 57, you stop there and 56 is the max you would use. You need to know signs of excess pressure - if you can easily open the action, there are no scoring marks on the bottom of the case or heavy cratering on the primer (but that can also vary on primer manufacture), you've got a safe max and if you stay in the load recommendation, you should establish it as safe.
Then load 3 bullets in the max load for each powder, the more powders the better, and hopefully, one of them should shoot well. From there, you can take the best load and tinker with that one. Generally, rifles tend to like a powder no matter how you load for it. So if you have 5 powders, you will load 15 bullets (5 powders x 3 bullets each) to establish max load, then another 15 bullets (5 powders x 3 bullets at max for each powder) to establish accuracy. So far only 30 bullets. You might say 2 powders look good so you load 3 more bullets for each of those powders for 6 bullets. 36 bullets establish a load is pretty effective. You can improve this a bit if you do some research on what powders seem to work well in certain calibres. H4831 is good in 260, 270, 280 and others. Certain powders seem to work well in 30-06, etc... You get the idea.
