I always had a problem with this joint in younger days. The problem is getting a hole in the fus. that exactly matches the wing section. Failing this, getting enough "filler type" glue in to fill the gaps. Putting plenty of glue on the wing and sliding the wing in place was never 100% satisfactory for me.
Eventually I developed a system :- Make the fus. and wing as per normal. If anything, make the hole for the wing in the fus. a bit undersize. As you slide the wing into place, note where it hits the fus., and trim a little of the fus. away, until the wing slides in with a reasonable fit. Take care to keep the wing angle of attack at zero or whatever. Then cut the fus. in half, along the wing centre line. Spread plenty of "filler glue" on the wing top and bottom where the fus. will sit. Add the top half of fus. to the top, and the bottom half of fus. to the bottom. Remember to put glue along the length of the fus. also. Stick a few pins at strategic points to hold everything in alignment and in place. Wind a length of 1/4" flat rubber, (F/F motor? [unlubricated!]) from end to end, or alternatively lots of tightish rubber bands. Ensure everything is still in line, and leave to set. Q.E.D.
This way you know you don't have any unseen gaps between wing and fus.
24hr. Araldite used to be an excellent "filler glue", in blue and yellow tubes, over here, (England). Sadly, we now can buy only a much thinner, runny, 24 hr. Araldite, in white and blue tubes.