A great place to buy a suppressor is from Silencershop.com. Huge inventory, great prices and very knowledgeable folks to deal with.
It's easy to do...
Go to the website and decide which suppressor you want then click the buy button. You can call Silencershop and ask for advice. Select the Class III dealer in your area you want it sent to. You're done. Silencershop handles all the paperwork for the transfer to your dealer. Usually takes three weeks or so for it to arrive at your dealer.
When your suppressor arrives at your Class III dealer, you then fill out your paperwork. Not much different that a 4473 you do all the time for a gun transfer. Your dealer should also give you two blank FBI fingerprint cards. Done
You'll need a CLEO to sign off on your paperwork. I just drop it off at the sheriff's office and they mail it back to me in a couple days.
Most police stations or crime scene departments will do fingerprint cards. Here in Chattanooga the crime scene team does it one day a week for free.
Make copies of everything. Write a check to the ATF for $200 and send it to the ATF along with your paperwork and both fingerprint cards. Done.
Wait a few months till your Class III dealer calls to let you know the Tax Stamp arrived. Go get your can and enjoy!