An easy, convenient way to farm K-Drive XP is right outside Fortuna. Exit Fortuna into the Orb Vallis, go left and go left again. You will find this pipe:
Jump onto it, grind across it, jump, do some tricks in the air, land back on it, grind across, repeat till your trick has a score of 3000 and land. This is the score limit per trick, regardless of what your multiplier mentions before landing the trick. This also limits your K-Drive xp per trick. Repeat till your K-Drive is maxed.