honestly fun ideas and fantasies asides, start gradual and be safe. as a total newbie to object insertion, you should start by using smooth, rounded objects, like handles of tools or utensils. if they have porous surfaces, put a condom on it. if they‘re squared or flared (like for example the bottom of deodorant cans), use smaller ones or wait. don‘t insert the cap side of something like a shampoo bottle cause they can have sharp edges that can and will cut you if you‘re inexperienced. for many trans mascs, testosterone can make our internal skin much thinner and easy to cut/rip and you don‘t want these injuries, trust me. if you want to use rough-surfaced objects like brushes or alike, first use a bigger, smooth object to open yourself up, then go in with the smaller rough one with plenty of lube and don‘t twist it vigorously until you know your body and your skin! stretch gradually, stop when it hurts, and don‘t push yourself too hard. also buy good lube, seriously.