Dr J58 makes a good point here about lubrication , and there are a few other things that come into play for both real life and play doctors out there.
As far as lubricant it's really a complaint on the part of the laboratory folks, basically a cover your butt tactic in that thier technicians may make an error. There have been a number of blind studies debunking this thought but it still remains out there. There is some truth - for instance in the thin prep use of lubricants with carbopol polymers may interfere. But even the thin prep manufacturer agrees that use of a quality lubricant will not interfere - surgilube, astroglide and I forgot the others they deem acceptable. I won't go into all the detail on slide vs liquid based paps but suffice it to say that a good gynecologist investigates what works best and acts accordingly. Also I mentioned this in another post - throw out those plastic garbage speculums, even well lubed they often cause painful insertion.
On speculum size , for point of discussion a graves model , a medium size should be right for just about any girl that is sexually active. Giving birth is not a requirement for a medium graves - using a small speculum and then twisting it around to find the cervix is going to be uncomfortable for your patient. Obviously there are instances outside of a virginal patient where a smaller speculum is required but realistically a medium is the best bet for the vast majority of patients. Patient position, depth of insertion and insertion technique round out the requirements for an exam that is not painful
Play doc advice in general - spend the extra couple bucks for gosh sakes on a good quality metal speculum and a large tube of surgilube if you really want your patient to schedule that next exam with you. Get her in the right position - butt off the edge of whatever you use for a table is a must so you have room to angle the speculum properly. Spends two extra minutes before you go at it - warm it up, lube it up, place a single finger in her vagina and press down slightly - these are the muscles she needs to relax for you - insert at an angle if you like turning horizontal as you insert - but don't stop half way as you will not find the cervix, hunting around for it is not going to be comfortable - as you fully insert you should gently apply pressure downwards - that is why the bottom of the handle is curved - it gives you a place to apply pressure - it was not designed this way without a reason - once fully inserted as you open the cervix will sort of pop into view between the blades and you should be able to lock into place with no discomfort. You should have a good idea of cervix position prior to insertion of the speculum so you know which angle the uterus is sitting and which speculum angle will be correct without adjusting -- there are a lot of videos posted out here so spend the time to watch ALL of them to pick up the best technique - the problem with training videos are that they were intended to go hand in hand with in person training - so not all details are covered.
Obvioudly I can't cover all this in a written suggestion and neither can a video or two - so go educate your self very well before performing your first, or next pelvic exam - you and your patient will both get a lot more enjoyment out of a well prepared technique
sarah