I’ve also done a video blog on the same topic which can be watched here on my OnlyFans profile.  I Know I forgot to mention a few bits, as I filmed it while waiting for my tea to finish cooking the other night.  So I will try and put this together in order.  

Before your session you MUST be clean inside and showered outside, if you need to you can do this at the venue – arrive with time to allow for you to complete it, otherwise that time will come out of your session … bare that fact in mind.  

The clean outside process is as follows: 
As the absolute minimum, you need to have a full body shower the morning of your session.  This MUST include the use of soap/body wash and shampoo.  Guys, you need to ensure you clean under your foreskin if you have one – I do NOT want to be presented with smegma slime or crustation visuals, not to mention that poor hygiene can lead to you getting infections.  Girls, be sure to wash your under carriage, and don’t use potent scented soaps or anything with sugars – these will cause you infections and bacterial vaginosis or BV, water is best.  
On top of the minimum as an ideal presentation of yourself.  Trim your pubic region front and back, either go have it done professionally at a unisex beauty salon.  Or get the scissors, clippers or beard trimmer/lady shaver on it – wet shave removal is optional, if you’ve never shaved the area before note it will itch as it grows back … DO NOT wet shave your ass, the potential for ingrown hairs is high and as you can’t see it, you wont know if they become infected, infected means a trip to the hospital in the worst cases.    
Lastly clean your ass properly after toilet visits, the paper should be clean on the final wipe!  If required used moist toileting wipes or a wet flannel to be certain you don’t have a shitty crack or skid marks in your clothes … I don’t want your shit on my floggers, canes, paddles etc.  

If you plan to have a session that will or might included anal, then the clean inside process is as follows: 
Having a poo the morning of your session is NOT acceptable, as clean inside!  That will only partially empty your bowel, and the rest will move through afterwards – if your session is to be humiliated and cleaned out that is different.  
Select you method of choice
1. Douching
2. Shower douching
3. Enema
4. Glycerin Suppositories
This is squirting water up into the internal part of your bum repeatedly, until it comes out clean and clear.  You want to use douch sprayer bottles, douch bulb sprayers or a shower hose attachment all are inserted anally.  You can get these from all good sex shops, chemists or online retailers.  
You can buy a variety of different complete enema kits, from pharmacies, some sex shops or online.  The process entails filling liquid holder with water or a fluid mixture of your choice (never use anything you wouldn’t consume orally!) inserting the hose nozel into your ass then hanging the holder (usually some form of bag), to allow gravity to do its job.  The fluid will pass into your colon and break down the content ready for expelling once you are full.  You can get safe chemical based versions in a bottle from the pharmacy, these are excellent at completely emptying you out and leaving you clean all through.  Word of warning don’t enema daily as you body wont get to absorb nutrients from food that are vital to your health. 
You can purchase these from any chemist.  These are a minimal option, they are jelly like tablets that you insert into your bum.  They cause you to go for a poo even if you think you don’t need one, and should be used within the hour before your session to ensure you have emptied out.  And clean yourself properly afterwards – no shitty ass cracks!!