that is going to take you FOREVER with a dremel lmao
Took me about 1.5 hours to cut a hole for a 3/4" bulkhead using a dremel. You could be working at it for over 3 hours, and the dremel glass bit is only good for aproximately 1/4" glass.
I'd just take it in and pay the $20 for somone to drill it honestly.
and buy your bulkheads first, then get the hole cut. they require different hole saws depending on the the brand/size.
if you want to risk cutting it first and buying your bulkhead later, here's a list I compiled a while ago. The one brand's spears (high quality expensive brand), and the other is the most common el-cheapo usually used in aquariums:
http://www.canreef.com/vbulletin/sho...light=bulkhead