A way you may find it easier to change a style at certain points in the song is to search the StylePicker and filter using the plus sign - + -. This limits the search to PG Music developed MultiStyles. MultiStyles increase the number of style changes from the normal 2 that display as blue or green. Most PG Music developed MultiStyles will have 4 or 6 sub-styles so that every bar you place a Bar Marker will also change the style instruments. Some instruments will be silenced and new instruments inserted into your song to replace the silenced instruments. This adds a lot of variety and dynamics to your song.
Bar Markers can be placed at any bar and can be used over and over. A MultiStyle with 4 Part Markers, each Part Marker will have 2 substyles (a and b) providing 8 style variations.
Any song can have as many as 24 Styles giving a total of 48 variations.
Here's some helpful videos:
How to find Styles that include more than two sub-styles
https://www.youtube.com/watch?v=F8rN68oTQqsBand in a Box Part Markers How To
https://www.youtube.com/watch?v=C6ViJ2691vU