Big-box and electrical supply stores sell a set of (usually) two drill bit extensions, about 4 feet long each one. These can be stacked together, to produce 8 feet or so of total length. The extensions are fairly flexible, allowing them to curve around corners to transition from a room to in-wall travel. They typically have a long-ish metal "chuck" on the leading end that can secure a drill bit using one or two set screws. You put the bit into place, tighten the set screws from the side, and hope that you've tightened them enough. Personally, I recommend you apply some thread-lock to the set screws.
The "pro" trick is not to just use the drill bit extensions. Get yourself something that is just the right size, like a tennis ball or raquetball (squash?). Or a golf ball, if the gap is really tight. Drill a hole through the center, and use the ball as a spacer to ensure your hole is drilled roughly at the midpoint of your space.
As far as "will it fit conduit?" that depends on the drill bit you choose. Doing this at all is a pain in the ass. Doing it twice to enlarge the hole would be a nightmare. So make sure you use a large enough drill bit the first time!