If you are in the first weeks: cold first, heat later. Perineal and breast compresses are the whole job at this stage, and the same pad covers both phases as things change.
If sex has started again and it hurts: a moisturizer for the tissue, and a lubricant for the moment. The moisturizer is here. For the lubricant, water based is the default, and nothing warming, cooling, tingling or flavored while tissue is still sensitive.
If it hurts at a particular depth rather than at the entrance: depth limiting rings. They stack at the base so penetration stops where you want it, and you add or remove rings as that changes.
If you are working with a pelvic floor PT: buy the graduated dilator set, not a single size. The progression is the point, and a set lets you move at whatever pace your body allows rather than the pace you hoped for.
On materials and safety: body safe, non porous, unscented. Oil based products break down latex condoms, and pregnancy is possible three weeks after birth even while breastfeeding.
Nothing here treats pain. If sex hurts, if you are bleeding, or if things are not improving, that is worth taking to a doctor or a pelvic floor physical therapist. We are not clinicians.