Start close. A big target will help. I usually suggest starting about 5 yards or closer and slowly move back.
I wouldn't think so because your draw length might be too short because you were using a release. If It Is just lengthen the draw length on the bow.
I have shot my Mathews with fingers before and it has a loop. It's easier to instinctively shoot without sights and no peep. But keep the rest. A kisser button on your string will help Also. It's tough but fun to practice that way. Tyler Rector BHOD
Instinctive shooting is a great skill to learn since a lot of your shots in hunting are at unknown distances. Not being certain of distances while aiming at game in the woods using sights can lead to a lot of missed shots. Here are a few links that I found helpful on you tube. Traditional Archery Basics Part 4 - Instinctive Shooting - YouTube Traditional Instinctive Archery explained by Rick Welch - YouTube Mathews Switchback XT Instinctive Shooting Tips: Part 2 - Team Fitzgerald - YouTube
The most important thing when shooting a traditional bow instinctively in my opinion is to really pull through the shot.