Assuming they have followed their aftercare, you will still need to cleanse the extensions and separate any 'stickies'. Brush through them with your lash spoolie and any that are ready to come off should fall off at this point. I use protein remover pads to swipe over the lash but be careful to not catch any of the lash bases. If you find that some of the lashes are stuck together then grab one with each tweezer and gently pull them apart.
Likewise, if any of the extensions are separated from the base or growing out, hold the natural lash firmly and peel the extension off. Be careful of how you pull them though as you don't want to damage the lash or cause any discomfort to your client. Always ensure that you are not pulling to much on the natural lash, that needs to be held in place.
When you're all ready to get started you can run through your lashes with primer or saline solution, whichever you prefer ( I use disposable lip wands for this).
Infills can be a little tricky when you are first starting out and you will find that how well your client has taken care of them will play a big part in how much work you have to do. I recommend to my clients that they never wear mascara and if they really can't live without eyeliner then it has to be an oil free one...AND THEY HAVE TO CLEAN THEIR LASHES!!! When I first started lashing I was far too lenient on my clients and I would spend so much extra time removing the makeup that shouldn't have been there in the first place. I was doing this free of charge and then doing their infills but now I'm not so forgiving.
My client's are amazing (mostly because I have weeded out the timewasters!) and I consider some of them to now be good friends of mine but at the end of the day they have to respect that this is your business and you do it to make money. My infill appointment for Classics is 50min and I book out an hour leaving me ten minutes to get them in and out before my next client.
Now that 50mins is all they get, if they turn up late or are wearing makeup when I've specifically asked them not to then that time is coming out of their appointment, not my time. It's not fair to make my next client wait. (That said, I understand that things happen and people can be late and I do accommodate clients that have genuine reasons).