Most Beach Cruiser bikes come with an 18 tooth rear sprocket.
Dandy to be able to pedal at 10 MPH without much 'keeping momentum' work, but they suck to get going and the high gear ratio kills the leverage to your hub coaster brake.
Just swap that 18 out with a 19 or 20 tooth for like $5 from you local bike store, they are easy to change out but you WILL need to do chain work, like a link or link and a half added to it.
But, the difference is staggering.
Not only does your coaster brake now work great enough to lay down an impressive skid, you can pedal up to speed and the leverage to start your motor is about 15 feet of pedaling ;-}
There is drawback however...
Should you find yourself out of gas or otherwise only able to pedal power it is like a little BMX bike, you can't get any real speed and have to pedal your butt off to keep what speed you can get.
In my book it is still a win-win-WIN cheap fix.
That last win would be one less handlebar control and at least for me, my natural instinct to pedal backwards to stop is still there.
One more tip...
If you go this way you will have to mess with the pedal chain, so it is a perfect time to do some chain matching and get the tensioner off your motor drive chain.
Even if you can't get an exact match you can put the tensioner on the pedal side if possible.
That is not as hard as it sounds either ;-}
You can use the kit tensioner ...
Or get fancy with a much smaller and more eye appealing one like this...
But regardless, in my book this is is the worst possible way to compensate for chain mismatch.
I am not on some sort of mission to stamp out drive side chain tensioners, but when you think about it I think you will get logic and I hope that helps you.