Hello, I use a 2 system as well. You can call it "Your System," "Appliance," or "Wafer & Pouch." Everyone on this site will know what you mean. It's not really necessary to use barrier film, only if your peristomal skin (skin directly around your stoma) gets irritated.
Removing the wafer.
I keep the pouch attached to the wafer while I do this. Using spray medical adhesive remover, I loosen the outer tape all around the stoma. Then switch to adhesive remover wipes to gently loosen the seal area of the wafer. Gently push in the edge of the wipe into the seal while carefully applying upward pressure. Never pull the wafer off! Hold the wafer and gently push your skin down with your fingers and use wipes. Take your time. The goal is to let the wafer fall off.
Use a remover wipe to wash away any residual adhesive around your stoma. Be careful not to hit or scratch your stoma. Be aware of where your hands are so you don't accidentally scratch the stoma with a fingernail. Stomas sometimes bleed a little; this is normal. I put the used wafer and pouch in the supplied bag found in my pouch box.
Cleaning the stoma.
Do NOT use toilet paper. Use moistened folded paper towels. It's not necessary to get it 100% clean. Just the big chunks. Taking a shower with the wafer and pouch off is great. Water will not hurt the stoma. Use a soap like Cetaphil that has no dyes, perfumes, or lotions. These chemicals will interfere with wafer adhesion. In the shower, I use wet, folded paper towels to gently rub chunks off the stoma. I put the stoma under the water stream to keep it nice and wet. I take 4 paper towels in. 2 for stoma cleaning, 2 for any stoma output. Face the shower and slightly bend forward when you shampoo/condition your hair. This prevents shampoo/conditioner from running down your stoma area. Be careful when drying off. You don't want to hit the stoma with a towel edge. I drape the towel around my neck to control it easily as I dry off my upper stomach area, neck, and arms. Pat dry the stoma area, don't rub.
Cutting the stoma hole in the wafer.
Get a portable full-length mirror to set inside your bathroom. Keeping an eye on your stoma for any "activity," use the provided measuring guide (should be in the wafer box). If your stoma is round... Lucky you. If it's oblong... It's a lot harder to match the cut hole to your stoma. It's said you should leave 1/8 inch all around the stoma. I leave more. If you cut it close, the wafer might shift after a while wearing it and rub the stoma. If this happens, your stoma will sting. Colostomy output is not super irritating to the skin. So some excess skin showing when you test fit the wafer is okay. As you cut the wafer, take your time, let your peristomal skin breathe. The longer your stoma is airing out, the better. I usually spend an hour. I could change the wafer in 10 minutes, but I don't. Make sure your skin is totally dry before you install the wafer. Unless you have skin problems, no need to use barrier film.
When the wafer test fit is good: Stand in front of the mirror. Pull off the plastic cover. Save the cover; this will be your fit guide next time you change the wafer. Carefully position and place the wafer over the stoma and against the skin. Press down the outer tape all around. Then put both hands on both sides of the wafer flange and lightly press down for a minute. Reposition hands at the flange top and bottom. Hold for a minute. Get the pouch. Check to ensure the drain at the bottom is sealed. Now you can add lubricating deodorizer to the inside of the bag if you want. I squirt it through the flange hole. Then work it around the bag, up to the bottom of the flange. I also coat the plastic opposite the flange hole. Looking in the mirror, I make sure the bag is straight down and press the flanges together at the top. Then snap the flange all the way around. I get a handheld mirror, pull up the bag, and check to see the flange bottom is properly connected. Put everything away. Tie a knot in the disposal bag, put it in regular trash. Get out there and enjoy your day.
PS: Everyone is different. I change my wafer every 7 days. Change bags 2 or 3 times a week. Just pop them off, put them in the disposal bag, pop on a new bag. Changing a wafer too frequently can damage your peristomal skin.