If you finance through a CC, then you should put that CC away and not use it anymore until the balance is paid.
This is because all payments are applied to the lowest interest rate balances first. Thus any additional regualr charges you make would be at the higher regular interest.
Example, you have a CC with an interest rate of 18%, but you pay the balance in full each month so you never pay interest.
They offer a low interest for balance transfers, etc at 4% so you use this to charge Disney
DVC. Your balance is $15000 for example.
You charge an additional $200 during the month as regular charges.
You pay $500 for the month, but the whole $500 goes toward the 4% loan balance and none of it goes toward the $200 you charged that month. That $200 then starts to acquire interest at 18% for the next few years, until the original low interest $15,000 is paid in full.
Every payment you make will apply toward the lower interest balance first before any is applied to higher interest balances. You cannot for example pay $500 and apply $200 toward the higher interest balance and the remaining $300 toward the lower interest balance.