As others have said, there is certainly availability so it is by no means impossible. My mum has been pretty successful in booking F returns to Rio, Cape Town, Phoenix/San Francisco and Johannesburg. On the other hand I was looking at Thailand for Christmas by couldn't get availability in F or J on the dates I wanted to a location near enough to make it worthwhile connecting.
The key thing is she is more flexible on dates being retired, whereas I am restricted to school holidays. You need to think not just about the destination but the region - if you were looking at LAS and there was only 1 seat available, you could go to LAX/SFO/OAK/SAN/PHX (not necessarily in F) and connect from there which gives you lots of options.
The other thing is to keep looking, as availability changes. 2 J seats are always released T-355days, but they often open up more F seats later on.
Finally, sometimes you just get lucky - I have a wedding in DC on a Sunday in August, and must be in the UK on the Monday morning; I looked up flights and the one I wanted just so happened to have F and J availability. I booked F out and J back, then upgraded to F both ways when I got more miles from flying and the availability was still there.
