One thing I haven't seen mentioned is what make of needle you and size of needle?
Most people are aware that the size (length) of the needle can make a difference to injection experience...
But the make can also, as different maunaufacturers not only use a slightly different lubicant on the needle but also how they've got the end of the needle can differ as well, from a straight cut across to quite a a slant... Might be worth having a look at this.. As some find that it really does make a difference indeed..
As to how many times one should or shouldn't use there syringes/needs and lancets before disposing well this is what I've always been told by my diabetic team over the last 21 years...
That you may re-use your syringes/needles they don't recommend that you use them more than 5 times in all... And if on insertion or injection is uncomfatable then dispose of needle/syringe... Same as with lancets..
As to injecting through your cloths, yes it's permissable to do so, but not advicable to inject through heavy cloth such as demin or through cloths that you've been wearing for a couple of days or that you work in more so if you are in a manufacutering type enviroment.... They also suggest that you only do this occasionally and avoid doing it as common practice...
I have always reused my syringes/needs (don't now as I'm on an insulin pump, so different set up) in 20 years of doing so I never had one infection or injection site problem, my husband does the same and in 31 years never had a site problem.. But for some people who suffer problems with injections sites, then changing there syringe/needle every time might be essentrail to limit problems..
Lancets, well I change mine when it hurts or I remember, I can carry out 6+ bg test a day, but looking at my finger tips you wouldn't know that I tested!
As to injecting through cloths neither of us has actually done this, as we just don't like the idea of it, but each there own..
When I was fist injected myself and for many years, I had to swab the injection site with surgical spirit as did all diabetics, until they realised that this practice could cause more problems with injection sites and infection as it dryed the skin, causing cracking etc...