Hi, today i found out that there is a super easy way to skill up Engineering fast and easy to get your favorite tinker below lvl 75.
It's all about Global Thermal Sapper Charge which you can learn @skill lvl 200 with a little trick.
Just level Engineering normally all your way up to lvl 425, learn Goblin specialisation and train Global Thermal Sapper Charge. If you don't get the tinker you've wanted, go and craft at least a few hundred Volatile Blasting Trigger so that you are prepared for your next rush.
Now drop Engineering and learn it again. Level until skill 200 and go for Goblin Engineering again. Since you already learned global thermal sapper charge before, it will autolearn again once goblin specialization quest is turned in, as in picture below.
[SPOILER][/SPOILER]
Now buy/farm a few Saronite Bars and go for another tinker! Don't forget to craft new Volatile Blasting Trigger if you're not getting your tinker again :P
I hope this will help someone, at least it saved me a lot of gold, i'm on my 5th try to get my synapses >.<
Source: Twinkinfo.com