Sweat rash can be really painful - sometimes it is a fungus happily living off what it finds on the skin.

Mixing a small amount of anti athletes foot powder into baby talc can often help, as can very cautious washing and dusting frequently - even if it stings the first few times. Wearing a kilt helps with this, its far easier than when wearing cycling shorts.

I make long garments - all natural fibre, usually cotton or linen and quite wide or split at the sides below the waist so they do not impede the drop of the apron. I use fine cotton to line the inside of the under apron in light fabrics, usually a pale colour toning with the colour of the kilt - it also helps to indicate that the kilt needs washing.

My personal kilts have (need) darts at the waist on the under apron and that makes a wider hem which tends to hug the lower body - in my case comfortably due to the long shirt/tunic/lining.

If the fabric is rough perhaps tightening the top part of the under apron would prevent it following the contours, or perhaps some tailoring/stiffening would throw the fabric forward rather than allowing it to fold inward - it can only be a matter of minor adjustment in the top of the apron to make a major alteration in the shape of the cloth lower down.