There’s one type of product for this, and the choice of which one belongs to a clinician. When caring for a stage I sore: if needed, use a moisture barrier to protect the area from bodily fluids. Ask your provider what type of moisture barrier to use.
That’s the whole of the direct advice. Wound Wizard can’t name a product, an application routine or how often to use it, and won’t guess.
What is clear is why it matters enough to have its own instruction. Not being able to control your bladder or bowels is one of the things that make a pressure sore more likely. The others are using a wheelchair or staying in bed for a long time, being an older adult, not being able to move parts of the body without help, having a disease that affects blood flow, and not getting enough nutrition.
Moisture also matters for the wound itself. With leg wounds, keep the dressing and the skin around it dry. Healthy tissue that gets too wet can soften, causing the wound to get bigger. Softened skin is how a wound grows.
The rest of the skin care for pressure sores applies here too: care for healthy skin by keeping it clean and moisturized, and check your skin for pressure sores every day. For anyone managing incontinence, those checks are happening anyway, which makes them easier to fit in.
One practical point about who to ask. A moisture barrier is the kind of thing a district nurse, wound nurse or continence service will have a settled view on, and asking gets you a specific product rather than a shelf of options.