transplanting is easy. let the plant dry out right before watering and get a bigger pot and fill the bottom with dirt high enough that your plants stem is going to be level with the pot. then tip your plant upside down, removed plant and place it in her new home. then fill the dirt around it. i dont like to fill the side dirt in before the plant goes in because the side dirt may fall in the hole before you properly seat you plant in there causing air pockets. then water. people use b-1 or superthrive for root shock but i never had and still do fine.

with your tin foil. is your closet painted flat white? if it is go with that and take that hobo home out. use your whole closet if you can. i did that for one grow and just used black plastic to keep the door outside light away

edit: when your putting in dirt you will want to gently press it down or after transplant/watering will push that fluffy soil down in the pot. but dont smash it down.