The re-bend does come naturally to just about everyone if they are taught to do the lifts right. Ive taught 200+ people to clean and snatch, ranging from 8 year olds to 50+ year olds and ranging in ability from good athletes who ended up on international teams to challenged athletes who will never be able to do more than modest weights… and EVERYONE I’ve ever taught has done a re-bend of the knee within a few sessions, the vast majority the very first session. It’s virtually impossible NOT to use a double knee bend if you are hitting the correct positions at the knee and at the point of the “second pull”. If you are going to hit these positions correctly, a double knee bend just about has to happen between them… thats why it doesnt normally have to be coached, becasue if you coach the top pull correctly, and coach lifting the bar from the floor correctly, the double knee bend happens by itself.
If you are having a problem doing the double knee bend… I would look a little closer at the position you are in at the beginning of the second pull, or in other words with the bar on the upper thigh just below the family jewels, or if you have shorter arms with the bar right in your lap. This is where the second pull happens. if you are a beginner, I’d suggest starting lifts in this position, sitting there a minute and really letting your body get comfortable with it and “remember it” then slowly lower the bar by an RDL type of movement down the thigh and to the knee, then reverse direction and do a lift. Having just been in a good second pull position, you will have a lot easier time going back to it as you do the lift. when you are comfortable with this, get into your second pull position, then RDL the bar to the knees, then use knee flexion to lower the bar to the floor… touch lightly then reverse everything to do a lift. if you slowly progress down your leg with this method, using RDL to get to knees, then knee flexion to get the bar to floor… don’t get crazy, but use a good controllable tempo with the lifts, and start each lift by getting into a good, solid and correct second pull position… then i bet you will be successful in teaching yourself to lift and you will be doing a second knee bend.