Here's a way you can turn your Ashtanga practice into a Vinyasa Krama practice for the day with the least amount of effort or confusion.
In Vinyasa Krama there are a number of Sequences, STANDING ON ONE LEG, TRIANGLE, LOTUS, INVERTED etc. Within those Sequences are sub-routines and in a sense Ashtanga is a collection of these Sub-routines brought together into a series. Within each Sub-routine each pose leads on to the next.
So, some ground rules that could be said to characterize a VK practice
1. Long slow breaths
2. Engaging of Bandhas at end of exhale ( with the exception of twisting asanas)
3. A slow pace to the practice
4. Very few jump backs and Jump throughs enabling you to keep alignment between poses
5. Occasional rests
6. Lead into poses
7. Engage Jalahandra almost throughout (except twisting poses and back bends)
I'll try to keep it as close to the Primary your familiar with as possible.
Before your first Surynamaskara take a moment to stand in Samasthiti and focus on your breath, notice where in your chest you are most aware of the inhale and the exhale. Allow a few normal breaths and then engage Ujaii. After a couple of breaths allow your arms to raise above your head as per usual in Sury A but link your hands and turn the palms upwards and stretch. Allow your arms to drop on the exhale and repeat a couple of times. After about four of these let yourself lightly forward bend on the exhale, not too deeply and then come up on the exhale. Do that a couple of times. Then go into your Surynamaskara as usual but at each stage hold the position for three breaths. So three breaths in Chataurunga and Up and down dog etc.
One Sury is enough. Now drop into Pada Hastasana or Uttanasana but stay there for about five minutes or ten long slow breaths. As a rule your inhale and exhale are the same but in a bend your inhale will be shorter(3-5 seconds), your exhale will be longer and slower (10-15 seconds), at the end of the exhale hold and engage the bandhas before releasing them as you inhale
Utthita tri konasana to Utthita Pasvottanasana is pretty much a TRIANGLE sub routine in Vinyasa Krama anyway, approach each pose gently a couple of time, going in a little deeper each time and hold the third time for 3-6 long slow breaths.
Utthita hasta Padangusthanasana is of course another sub-routine, practice as usual but with slower breaths. Carry on in this way to Dandasana
Once you get to Dandasana, lay down and rest for a couple of minutes in Savasana.
Comeback to Dandasana but before going into Paschimottanasana work into it a couple of times, bend on the exhale and come back up on the inhale, just working yourself gently into the pose. Now exhale into Paschimottanasana and stay there for five minutes or ten long slow breaths, if you want to, engage your bandhas at the end of the exhale but relax them as you inhale. Remember to keep jalahandra throughout.
Now take your Purvottanasana counter pose.
Work through the next section of Primary up to navasana as per usual but without any jump backs and jump throughs, make sure your breath is longer and slower, engage the bandhas if you wish on the forward bends, but not on any of the twisting poses.
Reward yourself with a jump back and jump through.
Take a rest in Savasana after Navasana
Continue through your Primary as usual following these principles, take a jump back and jump through perhaps in between sub-routines say, after Konasana but before the Suptas.
On into finishing as usual following the above principles. Spend a good Five minutes in Salamba Sarvangasana and engage the bandhas if you wish, likewise with Sirasana.
In Padmasana spend a good ten minutes on Pranayama, Kapalabhati 3x36, and then ten rounds of Viloma ujaii if you know them.
If you know any mantras now might be a good time to spend five to ten minutes chanting them
Take a more comfortable meditation pose if necessary and spend ten to twenty minutes in meditation on the breath
And there you have it. Obviously this is a much slower practice so may take twice as long as usual so you might want to drop a couple of sub routines or shorten them to fit it into your schedule.
Remember I'm no teacher and haven't been practicing VK that long, so this is no substitute for getting Srivatsa Ramaswami's book which will of course go into more detail and where you can see more clearly how some of the sub-routines are built up in a slightly different way. However, it should give you a taste for the different pace and focus of the practice though.