well, i've got a couple points that i think will help you a lot!
1) The first has to do with the examiner. Where a lot of applicants screw up is they forget that this is THEIR checkride. The examiner's job is to examine, not make decisions on how you do things or how quickly you do things. There is no time limit for any checkride. If you are given a bad vector, or are not ready for an approach, ask for a delay vector. If you are not ready for a hold, same deal. His job is to sit there...what about sitting there can he do speedily? First, there is no way that he should give you any hold that you have such a short time to figure out the entry that if you are efficient at drawing it out, you are not given enough time. Second, applicants also forget that he is also examining you on your decision making skills, not what method you use to determine hold entries. It shows very good judgement to take a few seconds to understand your problem so that you can choose a good solution.
2) The second has to do with your original question. Like anything in aviation, drawing holds takes practice. Have your instructor or someone else you trust knows how to choose hold entries effectively give you a TON of hold instructions. Draw and choose, draw and choose, draw and choose. The beautiful thing about drawing holds is that it gives you a graphical depiction of what you are doing. Its an outlet to organize a couple of items. Where are you in relation to the fix? Where is the hold? How should i enter it? Which direction am i going to turn first? THEN, as you are performing the hold...where am i in the hold? <- this last one sounds dumb, but it is really easy when you dont have a graphical depiction (on paper or in your head) to lose yourself as you are turning in circles. Lastly on this point, drawing it out over and over again forces you to think ahead of the airplane. What you are doing now is actually in the past, the decision has already been made and you are executing that decision. The biggest questions in instrument flying are:
Where am i?
Where am i going?
How am i going to get there?
Practice, practice, practice.
I guarentee, like pip said, that if you draw it out enough times, you will be drawing it in your head (instead of doing the thumb trick in your head)
