Hi,
Automatic debit position is used to post conditions entered in ID class ex. Dividend, Coupon payments. Manual Debit Position is used to post flows or update types which cannot be entered in ID class number (conditions tab), ex. charges related to coupon payments.
But based on your desired entries above; it seems that step 1 is an entry for accrual which can be executed via TPM44 and then the 2nd step is the actual interest payment which posted via TBB1 of which set-up may come from ID class number using condition type "interest".
Regards,
Chaikaru