I add to primary usually in one of those (I think it's muslin) fine mesh bags, hanging in the bucket with the cord held in place by snapping the lid over it.
Get some plastic or whatever surgical or kitchen gloves and put them on and dunk them in sanitizer when you're ready to bull the bag out, and squeeze the heck out of the fruit (held just over the level of the beer so you don't splash.)
Just did it with the blood oranges in my amazing
Hibiscus, Blood Orange & Sichuan Peppercorn Witbier.
It's a good idea to freeze your fruit before hand... I use a vacuum bag and foodsaver to seal it, crushing everything a bit to begin breaking the cells in the fruit. Freezing helps do the same thing, as well as POTENTIALLY killing off nasties. I thaw it for about an hour before I put it in the mesh bag in my primary.
Most of the time I've found that if I'm adding fruit to a secondary I'm doing it in a carboy, which means I'm putting the fruit in the bottom of the carboy and racking the beer on top...which means a lot more pulp and stuff... and with some beers that then means I have to rack it to a tertiary to clear that. (Found that with pumpkin when I used to add it to the beer post primary fermentation, rather than now when I add it to the mash tun and the boil.)
A mesh bag keeps the goop out of the finished product....
Or you could add the fruit bagless to primary.... like if you were fermenting in a carboy... THEN you'd be advised (based on experience) to rack the beer after to a secondary to clear.
So straight bag in primary, MUCH easier.