When watch videos, some players flip attack the underspin balls and some bump the balls forward. I am not sure what term to call it. It likes open the blade around 100 degrees and push/punch forward with  little lift motion.  

What are pro and con ?

Truth in advertising:  I do not regularly play with LP.  I do use it to help train other players in playing against it and have spent quite of bit of time learning how to play against LP.

The bump or pushing motion can be done quite aggressively producing a fast ball that still lands on the table because the underspin on the incoming ball becomes topspin coming off the LP.  The more reversal your particular LP naturally has, the faster you can hit the ball because it will have more topspin going back.  If you opponent plays well against fast topspin this may not be your best shot.

The flipping motion allows you to not only reverse the spin, but also add some topspin of your own to the shot.  However, you lose a lot of the speed your could generate with the bump stroke.  That is not necessarily a bad thing since a slower ball can create a timing problem for your opponent.  A highly reversing LP (especially OX) will not really add that much spin with the flipping motion so it may be most effective with LP with some sponge and more ability to generate some of its own spin.  I think this shot is a little more difficult than the bump since it is easy to brush the ball to lightly and have it just fall off the paddle and into the bottom of the net.

By using both of these techniques you can really mess up your opponent's timing.  If he expects the flip and instead gets the fast bump shot he can be late swinging.  If he is looking for the fast bump and you do the flip he will often swing too early and end up almost stopping mid-swing which will put the ball in the bottom of the net.  I have been the victim of this mixed attack with LP more times than I would like to admit.

I have also read some information on varying the spin on the bump shot by changing your timing of when you contact the ball.  Taking it early after the bounce on the rise produces one level of spin, taking it at the top of the bounce another, and taking it on the drop and hitting a little up yet a different spin.  I am not skilled enough with LP to really explain this in detail.

Hopefully a more knowledgeable LP player can add to (or correct) the above.

Mark

Let me clear these... What I mean Bump is not Pushing. Watch our friend PB player footage, 

Oliver.

https://www.youtube.com/watch?v=CRQQNNEwUSA

or Jian Li 

https://www.youtube.com/watch?v=jbk_yOHOyt0

When their opponents push, they open blades  little and bump out. The balls would go pretty quick with little top spin to opponent weak spots.

Some people still call that shot an LP push because it is done with a slightly open blade and is against underspin.  Of course the resulting ball is nothing like a push with inverted.  Perhaps the term "LP punch block" would be better but I have not heard that used. 

Depending on what LP you are using you might be surprised at how much topspin can be returned to the opponent.  Of course a lot depends on how much underspin they send to you with their push or chop.

When trying to teach other players how to play against LP's I am often surprised by the sudden dip of the ball when I use that bump stroke against a heavy spin push.  Sometimes it behaves like an even better version of my inverted loop against underspin.  I try to get inverted players to learn to push back with light underspin (or even dead) so that it is harder for the LP player to do a fast attack against their push.

Mark