In his defence, I'm new to custom moulds too and when I first got my SofterWear sleeves, I was clueless as to how best to get them in and out of my ears, so I was nursing sore ears for a while too. Now, I just pull the back of my ear back and upwards and slip the sleeve in with my other hand. They're in in a matter of ten seconds.
To remove, I pull my earlobe downwards to break the seal, then get some leverage under the bowl portion of the mould and gently tug and twist the mould forward, so the helix part of the mould breaks free from its locked position, and opening the seal in the ear canal. I continue the forward twisting motion, thus slipping them out.
I can consistently get a good seal and always get the same sound signature with these, as opposed to the hit-and-miss nature of using universal sleeves/foams.
Foam tips, in general, roll off the highs so your treble sparkle is reduced. They are good with sibilant IEMs as they can sometimes reduce the sibilance to a tolerable level. Silicone tips generally retain the low-end qualities of the IEM and also brighten high-end.
These are all generalisations; lots of other factors come into play such as insertion depth, whether or not you get a good seal etc.
I had a month break from the MG7s when my TF10s arrived. Back then, I thought, "woah, these UEs are da bomb! I can hear stuff in the high end I've never heard before!"
Then I pulled out my MG7s from their case. The TF10s now hardly get a listen :x