Short Answer: Yes he is. He is just so fast that the hand is back where he started before the opponent feels the impact. Thus creating multiple impacts in some moves like Jet Gatling, almost instantaneously.
What exactly is Gear Second?
Gear Second is somewhat similar to what in real life we call "Blood Doping". Luffy achieves this by leveraging the fact that is complete body and not just the skin is made of rubber. Thus his blood Vessels and Heart can sustain tremendous blood pressure that no normal human could survive. Using his Hands/feet as pumps, Luffy increases his blood flow in the whole body or just parts (Post-Timeskip)
Essentially Luffy increases the blood flow by forcing more blood through his blood vessels thus increase his fighting ability. This mode's enhancements to Luffy's physiology giving him the ability to use a new, stronger set of techniques which are generally the same as his old ones, but are so fast that even a skilled assassin would have a hard time actually seeing them
Source: Gear Second: Overview and techniques
Most of the techniques in this mode are named the same as the regular attacks with "Jet" added after the "Gomu Gomu no" prefix
These are just much much faster and thus have the incredibly high damage due to the impulsive nature of the impact. (Defined in physics as: A large force applied for a very short duration)
Also note the description of some of the moves.
- Gomu Gomu no Jet Pistol: Luffy delivers a Gomu Gomu no Pistol so fast that the fist's movement is invisible, and it truly seems like he shoots his opponent[..]
- Gomu Gomu no Jet Gatling: [..]Luffy stands still, bends forward and moves his arms upwards at speeds which they can no longer be seen, leaving only jet streams in their place[..] The hits land so fast that, after a volley, they seemingly connect simultaneously. The circles of air bursts from the punches surrounding Luffy, resemble the many barrels of an actual Gatling gun.
From these descriptions and analyzing Luffy's powers we can assume he has to touch the opponent for the desired effect. The attack you are thinking of is shown to be achieved by Bartholomew Kuma, who can use hi DF power to repel air using his palms.