Pulling bullets from some cases can be difficult if there is a sealant around the bullet. The fastest method I've found is to use a pair of plier type wire strippers - the kind with the strippers for various sized wire between the handles. Raise the cartridge in your press, grip the bullet firmly with the wire strippers, then lower the ram, and the bullet is pulled with little deformation in most cases.
Finding a powder charge for an unknown surplus powder is not difficult. Weigh the bullet from the cartridge, then weigh the powder charge. Find load data for that cartridge to see which powders are loaded to that charge weight within that bullet weight. This gives the relative burning rate of the powder, and you can safely work up loads using published data from powders with a similar burning rate in another cartridge. For an example, if you got the powder from a 7.62X51 cartridge, and weighing the bullet and powder charge showed that it was consistent with data for H-4895, you could safely work up a load in say a .30-06 using H-4895 data.