There are other signals!
I use "hit fist on top of helmet" for emergency situations.....for instance, cop ahead, accident ahead, other emergency vehicles, and/or as a way to warn somebody to slow down quickly as there is immediate danger ahead.
I used to use (and sometimes still do) the lean over and push hand to the ground for folks to slow down, but many of them do not know what that means these days.
Riding with other folks, I use feet for pointing out debris on the road. Point at gas tank for gas, thumbs down if you need to stop, pat my stomach for grub, this motion

for needing some female companionship,

for a naughty girl, stand up and do a crotch grab for a car load of hot ladies, and so on. Yeah, that's right, I AM A GENUIS!
__________________
~Jason
San Diego Riders click here >>>>
San Diego County Area Riders (SCAR)
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1998 VFR800
Two Brothers CarbonFiber Slip-on
ZG Double Bubble
Oxford Hot grips
BMC Air filter
Thurn Motorsports Aluminum Chainguard
Knurled Aluminum Footpegs