I took a 42A job after being 7 points off on ASVAB from getting a my preferred 35M. How quickly can I bump up my score and reclass?

This is unclear. 1,. Did you enlist for the 42A, and have you been sworn in and or in training for the 42A. 2. There are no JOBS in the military, this ain't no 9-5, quit when you want to. There are classes offered to improve your GT score. You can find classes to improve the weak areas of your ASVAB. This will take time. 3. Depending on whether you are Active, Reserve or NG component, will decide the easy or reclassing. Normally, if you are in training and or in a unit, you aren't allowed to reclass till 1 yr prior to ETS, unless you are going into a critical shortage MOS. A retention/re-enlistment NCO should be able to guide you on this.

In this case I would have waited for enlisting, study hard, retake ASVAB and get MOS I wanted. But it's just my opinion..

Changing your MOS is extremely difficult. Once you sign a contract you are bound by it. It is like buying a car and then saying you really didn't want it. You can raise your GT score but once you are in the only way I have seen anyone reclass is by re-enlisting or if there is an overage in your MOS and a shortage in another MOS. Besides that I hope you like paperwork.