Ma long is consistently in top 3 players in the world.  Here is an hour long video in which he presents his technique followed by explanation and critique by a Chinese coach.
01:02 04:04 – Short FH (Forehand) Serve
04:55 06:58 – Long FH Serve
07:57 09:40 – Short BH (Backhand) Serve
11:11 14:14 – FH Drive
14:57 17:42 – BH Drive
18:13 22:14 – Alternating FH and BH Drill
23:44 25:27 – Service Receive: Push and Attack
26:22 30:24 – BH Flip
31:29 34:16 – Looping Semi-long Returns
35:29 37:44 – Over The Table BH Loop
38:55 40:54 – Attacking with FH and BH
41:34 43:39 – Initiating Attack with BH
44:52 48:10 – Two-Winged Loops From Near To Mid Distance
50:27 54:19 – Smashing Lobbed Balls

Transcripts of some sections I found useful

Looping semi-long returns (transcript) of section 31:29 34:16

Looping serve return down the line

The trajectory is produced by an upwards and forward action. It can’t be just upwards.
It is necessary upon the contact with the ball, to feel like you’ve gripped the ball before you loop in the forward motion.  If you can grip the ball, if you meant to loop it short, make it as short as possible. To make down the line shot contact point has to be later.  If you were going too fast at it, down the line shots are impossible.   When you slow down, the racket angle will be more opened, and down the line shots will be possible.

Looping serve return cross court

During the receive of serves normally the player will spring up slightly.  Before he starts to move, center of gravity must be low, when it’s a return to your forehand extremity pocket (close to the net forehand area ?).  The center of gravity must be low. You needn’t impart speed.  Actually the slower it is the better.  The importance lies in being able to brush the ball.  For semi long returns, you must be able to slow your pace down.  Only then will you have sufficient time to brush the ball. Also sometimes…, racket angle must be controlled well.  The racket face must not be overly closed.  If the racket angle is too closed, there might not be enough brush on the ball. If the racket face is too opened, there’s a tendency to flip the racket making brushing difficult.  The racket angle has to be adjusted to a suitable angle.

Coach’s summary

Ma Long’s forehand position loop of long backspin returns.  When the weight is on the right foot, during back swing you must drop your shoulder.  The forearm must be lowered sufficiently. To create some distance between the ball and the racket. Strong spin must be imparted.  Due to the placement of the return, the part of the ball to contact should be the lower hemisphere of the ball.  This shot requires the right foot to be firmly planted.  Power must be focused (applied in short span of time).