I have a very difficult colostomy, an innie that cannot even be seen from the outside. I have the same problem you do, having stool collect at the site and on skin instead of bowel tissue. That pooling stool causes abrasion and bleeding that is also very painful. I also have the trouble that appliances don't tend to stick to my skin for more than 6-12 hours. Here's what I have discovered through trial and error and also my Ostomy nurse.
I use a convex barrier ring and then fill in the back side of that with stick paste because the barrier ring and bag glue will not stick for more than 12 hours but with the sticky paste around the outside curve of the convex ring, I get good stick for about 48 hours or so. The biggest help with both healing and getting my skin to allow for sticking is something called Cavilon made by 3M. Its reference number for your pharmacist is: 5051 (NOT 5050, that's the big one! Not sure if you're in Canada or if that makes a difference in the reference number, it shouldn't).
Cavilon is a liquid product that comes in two sizes, you would need the smaller one (Cavilon advanced skin protectant, 0.7ml sponge tipped applicator). You break the ampule within the handle of the plastic applicator, the small amount of liquid then suffuses the sponge attached. You then swipe it delicately onto the abraded and bleeding skin, putting one coat on. Don't push hard, just a thin coat. Keep the skin taut and don't touch anything to the moist skin for 60ish seconds. (It sticks to itself and everything else if you do). All of this is done on clean, dry skin with NO OTHER PRODUCT on your skin at all. After the 60ish seconds, you then apply your convex ring with bag (I build it all together then apply all at once with heat from a small heating pad. The heating pad is awesome - cordless too. Here's a link to Sunbeam Goheat heating pad https://amzn.to/3skMVVR).
Cavilon is expensive, especially here in Canada, but I did get special coverage after applying. I hope this helps, there was nothing that truly helped much at all except silver powder but then the Cavilon barrier became necessary as my Ostomy is just that bad.
If you cannot get Cavilon or it's too expensive, the only thing that helped before was AG+ Silver Powder advanced wound care by Medline Reference # MSC9405, 5g bottle. You use it like you would stoma powder. Clean dry the area, put silver powder on, brush off excess, spray with no sting skin prep spray (I use Smith Nephew), let dry, then repeat the process but you use a coat of your regular stoma powder instead, brush off excess and respray with no sting skin prep. This is called "crusting", doing two layers. No need to use two layers of the silver powder, it's too precious for that, the first layer of silver powder and spray is the barrier that helps healing, the second layer is just more protective, not healing like the silver powder layer. Hope this all helps.