Twist the top off of your spray bottle. What you will need is the nozzle and the plastic piping behind it as a connection point.
Clip off a two inch section of the plastic tubing attached to the nozzle and set it aside.
Drill a hole in the nozzle piping equal to the size of the rubber tubing and glue the tubing into the hole. Be careful that you are not blocking the piping with the glue. The glue can get into the straws and harden, making the materials hard to pass through.
Drill two holes into the bottom of the film canister. Make your holes equal to the size of your metal straws.
Glue each metal straw into a hole. Again, be careful not to clog the straws with the glue.
Position one straw so that it is low in the canister. This will be your paint intake. Set the other as high as possible so that the cap will still fit onto the canister. This will be for the air. You cannot fill the canister any higher than the tube sits, so place it gently.
Pull the cap off of the old marker and take the tip off. Try cutting it off with heavy-duty scissors or using your razor. Cut off the back end as well, so that you have just a plastic tube. Remove any ink packets or tubes from the inside of the marker.
Drill holes near each end of the marker tube and another hole in the center of the marker tube. Drill the holes at an angle so that the drill points will point towards the end of the marker. The holes need to accommodate your plastic tubing, but will not be sealed.
Line the film canister with your center marker hole and glue it to the top of the marker with the drilled holes positioned at the bottom. Make sure that your canister does not cover the center hole, but that they are lined up together.
Pass one of your piece of plastic tubing from the end of the marker and out of the center hole. Attach one end of tubing to the metal straw that is lowest inside of the canister. Glue both together to form a seal. The other end of the of rubber should meet with your nozzle. Seal these together with glue. They have to be air tight.
Attach a second piece of tubing to the small plastic pipe behind the nozzle. Let the remainder of the tubing pass through the marker tube, so that it sticks out on the end opposite of the nozzle.
Attach your last piece of tubing to the metal straw that sits high in the canister. Let it pass through the hole you drilled in the marker that is on the opposite side as the nozzle.
Fill the canister with paint, being careful not to fill any higher than the metal air straw (this is the straw the sits up highest).
Blow through both tubes at the opposite end as the nozzle at the same time onto a piece of paper or a plain T-shirt. Use paper towels in case a mess occurs.