Many soapers say that beeswax in soap also helps prevent ash. I don't use it often, but if I remember correctly, the soaps with beeswax did not get ash. But to use beeswax, you have to soap hotter because it has a high melting point. And the percentage often recommended is approximately 3% of your soaping oils, so you don't want to use too much. It can heat up your soap, too, so getting the soap in individual molds might be less of a struggle with 3% beeswax. BUT, if you use beeswax, you probably won't have time for intricate swirls. Technically, you probably can pour while still at a thin enough trace as long as its a fairly small batch, but that may take a lot of practice before you become adept at pouring before it is too thick.
However, if you don't want to change your recipe, there are some other things to try. Some folks spray with rubbing alcohol only once right when they first pour the soap. However, the Soap Queen recommends spraying 3 times at 20 minute intervals as the soap is cooling using 91% rubbing alcohol. I have also read for one soaper that what works best for her to prevent soda ash is to spray after the soap first comes into contact with air; that is soap that is kept covered until after it gels and cools.
For a smooth surface in individual molds, the best solution for me was to fill all the way to the top and use a skinny spatula to smooth the surface (like smoothing cake frosting on a cake, but with thinner soap batter). THEN, I plane the bottoms of the soaps. This is what works best for me with the problem on not getting a perfectly smooth surface on the bottoms of the soaps.
Some folks cover the molds with wax paper to keep the top (which becomes the bottom after un-molded) smooth and the air away from the soap. I have not used waxed paper, but do use plastic wrap, which does often create a wrinkled surface. Planing makes the surface smooth.
To gel my soaps in individual molds, I place them on a cardboard tray lined with a towel or silicone mat, then cover with plastic wrap (after misting with alcohol), then cover with a sheet of cardboard, then cover with another towel draping it over the top and sides. I may or may not invert another carboard tray or box over top of the whole thing to create a mini-environment. Then I put it all into a pre-heated oven. I usually pre-heat to 150° per my extra oven thermometer, turning off the oven when I put the tray of soaps into the oven. I sometimes stack more than one tray of soaps on top of each other in this fashion. They tend to help insulate each other when stacked. The cardboard helps insulate as well as providing a rigid surface above and below the molds. The towels help insulate as well. How long I leave the soap in the oven depends mostly on when I put it in. If I put it in as night, I leave it overnight and remove the next day. If I do it in the morning (which I rarely manage), then I would leave it in all day. There are alternatives to using a stove, such as using a heating pad, etc.
