You've probably heard of "Imperial" as it tends to be very popular among wildcatters. I've used it and Hornady's Unique. I prefer the Unique as it costs less and does the same job (in some cases better). Since Redding bought out Imperial's formula and they (Redding) now distribute it, the price has nearly doubled. Unique has been around a while, but it does the job as well.
I like the wax sizing lubes, as they are a LOT easier to work with and don't leave a lot of mess. They also have the added plus of putting a little bit of a sealant on the brass so it doesn't seem to tarnish as fast.
You normally don't put it inside the the neck of the case. You use it on the shoulder and base of the case. Just dab your finger in the imperial wax and smear it on the case. If you can see it on the case, you have too much. The only time I use imperial wax inside the neck is when I'm expanding the neck. I hope this helps.
Typically, I'll use a q-tip and get a little on it, then put it inside the case neck. You'll only need a little every couple of cases or so (once it gets on the expanding ball it'll work for a few cases before having to lube another case). You'll feel when the expanding ball gets a little stiff on the down stroke, this is a good sign to lube the next case neck.
The larger the caliber the harder to size so on my 300wm 338 and 375 I bought Redding carbide expander balls they make them for there own dies and RCBS on the other ones like 30-06 and down I either dip every 4th or 5th case neck in mica or make sure I shoot a little Dillon in the case mouth on every 3 or 4 cases.
I have tried every case lube out there and the Dillon is the best and easiest to use plus a bottle last forever.