Trading for picks?

I found this incredibly difficult to do. I was rebuilding with PHX and tried to trade away a lot of players for picks, but found it hard to do.

Is there a certain time period (like Jan) that I should be trading for picks? Is it really difficult to trade for the picks of the worst teams?

Usually after about 2 months from the start of the season, teams will start to grow interest in trades for picks. If you're looking to recieve the pick instead of trade it away, I've found it much more diffifult. Also only some teams are interested in trades for picks. When trading, look at your pick (if you're trading it away) and look at the interest bar. If the interest bar is empty, you stand no chance with trading a pick to that team. Good luck.

Is it really difficult to trade for the picks of the worst teams?

Yes, absolutely. You're not going to get a lottery pick for a handful of scrubs, you generally have to give up a star player for one and even then there's no guarantee they'll be interested.