"Anyone know some of the different techniques for aiming without sights?"
Here's just anothet hot-air opinion. As already mentioned there are any number of ways to shoot an arrow. Perhaps the easiest to achieve accuracy with quickly is to shoot three fingers under the arrow using very lightweight arrows...basically just looking down the shaft at the spot and 'gunbarreling' or "Apache drawing", as its sometimes called. The sighting approach is straightforward and works especially well for beginners. Lightweight arrows remove most of the guesswork re trajectory. Effective and easy, but not for everyone. Or you could use the more technical approaches as mentioned above...point of aim or (more popular) gapping...the latter similar to shooting with a sight since you calculate/blend/calibrate distance with your sight picture and with the tip of the arrow to 'aim' the arrow. Again, potentially effective with trial /error /practice, but again not for everyone. Or, you can shoot 'instinctively' ...basically just mentally centering the spot you want to hit in your sight picture and allowing learned repetition and 'what you see' to make the shot with no concious calculation of yardage and using no artificial sighting aids. Probably the least understood method (and most maligned), but nevertheless effective for some.
One thing is always required regardless of the method...developing good form FIRST. Thats probably the most overlooked ingredient in the shooting recipe. Form must be a good 'fit' for the individual, absolutely repeatable from shot to shot, and be engrained in the brain (automatic...like breathing) before expecting much for consistent results. Form is, above all else, what decides results.
If your preference or inclination is to measure and conciously 'maneuver' your shot then gunbarreling, point of aim or gapping seems like a logical choice. If you prefer to make your shot more or less subconcious (no thinking or calculating needed...look and shoot) then instinctive makes sense. The first two probably will give you better target scores, the third is perhaps better under close hunting conditions where shot opportunities are close, occur fast and allow less time (physically and mentally) to make the shot.
An intangible to consider is whether your urge to shoot barebow is fueled by a need for optimum accuracy (where sights and/or a calculated method makes sense or feels best) or more by a challenge to do it 'naturally' without relying on mental or actual sighting aids (where instinctive fits well). A personal decision.
Good luck.