For a first time builder, glassing can be quite intimidating and doing the inside deck is a good practice area.

Just realize that glassing an interior is substantially harder than glassing the exterior. Brushing or squeegeeing the cloth on interior pulls the material tighter which can result in "bridging" where the cloth lifts off the surface. At worst this will cause bubbles, at best you end up with more epoxy than necessary.

On the exterior, just about everything you do, pulls the cloth tighter against the surface and gravity is working with your to minimize the amount of epoxy you apply.