I use custom styles most of the time and do all dirty tricks to have the fills I need. I started as a drummer; maybe that's where the obsession comes from. On PA80, I program even intro1 and intro2 as fills. I like it because, then I have two fills that I can jump into at any time of the measure (fill1 and fill2) and two fills (intro1 and intro2) that can be synched with the start of the next measure. If needed I would program end1 and end2 as intro and end. If I need a fill just before a perfect cadence, I would hide the fill in a chord variation and assign it to 7sus4 and try to hide 4th note with right hand playing; doesn't work always, but most of the time. Sometimes I put percussion in the drum track, put the fill in the percussion track, and mute the percussion track. At the right time I unmute it to get the drums-only fill and mute it back. I do not do all the tricks at all the time, but as the need arises.

I know this is really non-standard, but when the fill-ins are very specific and generic fills wouldn't work, these tricks really work for me.

Shiral