How do I use LOC account?

I've spoken with my accountant regarding possible set-up of a LOC account.
Some for personal, majority for investing. But they cannot give me any more of an idea as to the ins n outs as I already know.

As to not get the amounts mixed up, and without creating two accounts (headache and costs involved) how should I set up an account if I wish to withdraw this equity?

I would use it only when needed or wanted and leave it offsetting the loan balance. Would not contaminate it with my own funds for tax perspective.

Is it o.k to use some funds for non deductible and some for deductible stuff so long as its recorded well in your paper work and transaction history/labelling?

Would it be best to top up an existing loan, or create a new loan for this purpose?
How would/do you do it?
I'd personally be taking out 2 facilities. Recording the expenses maybe one thing but when it comes to aportioning any repayments down the track the fun will start. I would hazard to say that your accountants bill would increase by more than the initial set up costs (making 2 LOC's).

Depending on the lender, it maybe worth taking out a pro pack to minimise costs if you don't already have one.

Thanks guys,

Would it cost me more to create two accounts?
I have a premier advantage package from this lender.

I'm kinda worrying about what I do years down the track, just keep creating more and more accounts? Or would I just extend the two existing accounts with that lender? Or, is there a whole swag of options awaiting? I just want to do things the best way possible for now, and into the future.

The lender I want to refinance with is Westpac for LOC facilities. Its the lender I have most equity with for one single property so no cross collateral or anything.

I already have one small LOC with Westpac and that was extended to purchase another property (was a variable portion for original loan and is now $40,000 more than it was since I refinanced it and purchased another property). I'm thinking I could "up" that one again for the tax deductible stuff (when I'm ready to use it) and create a totally new account for non deductible stuff, what do you think?