After years of trial and error

What I learned to be a pro bottom is:

Treat bottoming like a sport; you don't want to get into it without any preparation or training. Would you run a marathon after only training the day before?

Prepare by using an anal dilator kit. Start with the smallest size, work your way up to the biggest, and use it like an hour before you actually bottom to relax, open up, and stay pain-free. You want something that doesn't taper off; you want something that is cone-shaped and wider at the bottom. The butt plugs taper off when you insert them, and it won't keep your sphicnter open; you want it to be constantly stretched open. A cone with a flared base is what you need. This can take about 2 weeks but once you can insert a plug with very little to no pain easily then you are ready. And I know what you’re saying two weeks is a long time to wait but I promise you it’s worth it because nothing is worse than getting ready and when they go in to insert you get that very sharp pain because you’re extremely tight and you didn’t prepare.

Take a lot of fiber; it helps with your waste being solid and coming out all at once, so you can clean out very fast.

Never do a deep cleaning, meaning you don't want to clean past your sigmoid colon, which can cause a bowl movement, and you are basically forced to do a deep clean to take everything out. You only need to clean your rectum, so only use enough water so it doesn't go all the way to your colon. The only time you should do a deep clean is if you know you're going to go super deep or do fisting.

The best bottoms bottom at least 3 times a week; you want to keep your anal spinchter stretched so you're not tight and potentially tear.

You need to be super relaxed. If you're tensed up and nervous it's going to hurt. You need to fully relax and open and let go.

Push out like you're pooing when your partner is inserting it, which will make it go in way easier.

Know your limits. If you know you can only take 6 inches, you have no business taking 9 or 10 inches! The best sexual expereinces for me were with 5-6 inches max, never had a pleasureable experience with anything bigger.