Disposable plastic spoons are excellent for spreading fillets into joints. Work well for mixing epoxy too.
A Foredom rotary tool was indispensable for me. More powerful and durable than a Dremel flexshaft.
I fabricated his & hers cabinets that I mounted on either end of the bulkhead. The shelf can hold only so much. They secure personal objects inside the camper too. Mine are 10″ 12″ x 4″.