I really try to follow the KISS rule and keep things simple when starting something new. You can graduate later into more skills. In Cozumel it's pretty clear water. To start with your new SMB, just go to the local Home Depot and get a 4 inch long stainless steel eye bolt. Buy some braided line and measure out 15 feet (safety stop). Wrap the line around the SS bolt and then roll that all up inside your SMB. When you get to your 15 foot stop, unroll your SMB and let the short 15' line fall down below you (it won't hit the sand below). Inflate the SMB and the eyebolt below will come up and stop right infront of your chest on the safety stop. Then wind it up as you slowly ascend.
You don't have to worry about holding a spool, or snagging a reel, or losing your SMB. It's keeping it simple. After your trip you can keep or trash the total of $4 you spent on the bolt and the line and then decide on a reel or spool for deeper work now that you have practiced the inflation part. The biggest problem with inflating SMB's for most people is getting air inside the SMB,,,,and then grabbing the reel or spool. Make it simple, get an SS eyebolt, they work simply and you want to keep it simple, then graduate to a reel or spool.