Well lets be clear. The language can be a bit confusing.
Auto
When the Solo is doing all the flying (including an Auto mission, or Auto landing). In Auto, the solo uses GPS and its other sensors to fly to way points, or do things like an Auto landing.
For some reason, the few times I've allowed Solo to *Auto* land, its exhibited bad behavior. Usually hopping/bouncing on the ground, which could easily lead to a flip.
Fly
For those of us who flew 3DR before Solo, this used to be called "Loiter." This is a mode where the Solo uses GPS to hold its current position, uses the barometer to maintain altitude, uses the compass to maintain heading, and uses the IMU to stay level. This is the easiest mode to fly around in because as soon as you let go of the sticks, the Solo will stay in that spot (it will loiter in place).
Manual - before the Solo, this was called "ALT Hold." In this mode the drone does not use GPS to hold its position. It will drift with the wind. It does use the baro to hold its altitude (thus the original name "Alt hold"). And it keeps it self level (using the IMU). For the record, there are additional manual modes (like stabilize, sport and acro).
Then there is "Landing Manually"... this can be confusing because we don't mean that you switch to Fly:Manual (aka Alt hold) and then land. We mean that you stay in the GPS assisted Fly mode (aka Loiter), and then land yourself (manually) using the sticks on the controller to set the Solo down gently (keeping the left stick down until the motors shut off). This manual landing is still done with the benefit of GPS in Fly mode to help you fight the wind and keep your position.
The reason why a lot of us land "manually" while in Fly mode, is because Auto Landing seems to lead to so many accidents and tip overs.
There are folks (mostly old timers), who will tell you that you should always take off and land fully manually. These guys really mean that you should be in a true manual mode like Fly:Manual (aka Alt Hold). I used to recommend that myself. It avoided sudden accidents caused by gps glitches. But I don't recommend that anymore. The Solo has enough redundancy built in, that even if you lose GPS near the ground, it won't shoot off like older drones did.
So to sum it up, to "land manually":
- Keep your Solo in FLY mode.
- Reduce altitude slowly until the Solo is on the ground.
- Keep the left stick down until the Solo detects it is on the ground and shuts off the motors. It may take 3 to 5 seconds.
To take off "manually":
- Keep you Solo in FLY mode.
- Push up on the left stick.