Medals can only be earned in Career mode, and progress towards them can only be checked in-game by hitting Start and scrolling all the way to the right. Most of them will come naturally, though some require grinding.
Low-level scope kills can be farmed with the two largest rifles on the first elephant hunt.
10x and 20x scope kills can be farmed with smaller calibres. Use the mountain goat or the antelope hunt, or whatever strikes your fancy.
The easiest way to find blood trails is the first elephant hunt. Wound the animal non-lethally so that it flees, then kill it before it escapes. Now run along the trail it fled, and depending on the distance it ran, you can find up to four finds.