Private Party Trade Question

I a trade between two private parties, a long gun for a handgun, what would be the best method of trade? 

Would it be for the party receiving the handgun in the trade to first apply for the permit to acquire the handgun with the serial #number and all the info,
 Then two weeks later make the exchange at the HPD?

Hypothetical: If the party applying for the handgun permit does not actually receive the handgun, i.e. the owner reneges on the trade, 
what does the person with the permit to acquire have to do? or what should they do?  If you have a permit to acquire a specific  handgun and are not able to register it because you don't have it...?

The person with the permit has 5 days to register the handgun once acquired, but what if they never acquire the gun?     Thank you in advance for all your help.