If you have unsightly issues with your swirl plaster ceiling, the easiest thing to do would be to sand down the areas that have damage and re-swirl to match the old swirls. You may also opt to just eliminate the swirls altogether, depending on the number of blemishes. Below is a guide to help you repair and restore the swirls.
Step 1 - Sand Down Damaged Areas
You want to sand any problem areas down to a flat surface. Prepare the room by removing all furniture or pieces you do not want to get dusty. Then put drop cloths down on the floor for easy cleanup. Use your electric sander to go over all the raised areas and parts you are having issues with. If you wish to sand the whole ceiling or a large area, it may be wise to close off the room with drop cloths.
Step 2 - Prepare the Joint Compound
The joint compound is going to be used to redo the swirls on the ceiling. This is a mixture of joint compound mix and the paint used on the ceiling. Fill your 5-gallon bucket with a gallon of paint. Then slowly mix in the joint compound. Mix thoroughly until you get something that is roughly the consistency of peanut butter. It could be a little bit thicker.
Step 3 - Add the Swirls
Use your paint brush to apply the thick mixture to the ceiling in a swirl pattern, just like the existing one. Try to mimic it as much as possible. If you are working a large area, try to pause for a minute so that the swirls dry and you don't continuously flatten over them. Repeat this for every problem area.
Step 4 - Finishing Touches
If you have a noticeable difference in color from one set of texture to another, wait for everything to dry and then just put one paint coat over everything. If there are areas where the swirls did not show up well, feel free to add a second or third coat until you achieve the desired look. Adjust the paint brush size to accommodate the size of the swirls. Doing so will make a big difference.
Step 5 - Clean Up
Take all of the drop cloths to their necessary disposal zone or washroom for reuse. Then dust the area and vacuum it to reduce allergens.
Step 6 - Eliminate the Swirls
If you want to just get rid of the swirls entirely, put a coat of primer sealer over the ceiling after you have sanded down the raised areas. Then take a wallboard knife and use it to coat the entire ceiling with wallboard compound. Sand it to a smooth finish once it's dry. Then cover it with the paint of your choice. Use the same cleanup techniques as above.