honestly, i wouldn't sell anything at this point---bitcoins or altcoins. anyone who waited this long has already seen the worst of it. selling now might not be the absolute bottom but it's highly likely you'll lose coins if you plan buy back (or miss the trade if you don't).
i prefer long term holds that i can "set and forget". i can't tell you how many coins i'd nearly forgot about that doubled, 10x'd or better. you won't get that trading on bitmex because you're paying swap interest or holding limited duration contracts, and you basically only have access to markets for the very top coins. my biggest gains in altcoins have always come from low caps that would never trade on bitmex until after most of the gains are gone.
i occasionally trade the pink sheets, particularly pot stocks, for the same reason.